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The Delta Codex
A girl whose subconscious contains dangerous ancient knowledge finds her voice in this gripping middle grade sci-fi fantasy perfect for fans of Diana Wynne Jones and Scott Reintgen.
Is there safety in silence?
In the city of Danak-Tol, children known as codexes are chosen to safeguard echoes—fragments of ancient knowledge too valuable to destroy but too dangerous to use. Forbidden to speak lest she accidentally release her echo, codex Delta lives a lonely life. Still, she knows she must obey the wardens’ strict rules to keep her home safe from the vicious beasts, heretical Scrappers, and toxic blood storms that lurk beyond the city walls.
But when Delta breaks her vows to help a young girl escape a blood storm, she begins to have strange dreams, which lead her to question everything she knows to be true about herself and her city. To find answers, Delta must journey to the one place she most fears: the wasteland beyond the walls of Danak-Tol.
Together with her small but feisty mechanical companion Flick, Delta dares the perilous ruins of a long-abandoned skyship, the gullet of a ravenous sphincter worm, and even befriends a young Scrapper named Drii. But all these adventures only lead to more questions. What is the true danger that threatens her entire planet—is it really her echo, or is it the silence that has imprisoned the truth for so long?
Is there safety in silence?
In the city of Danak-Tol, children known as codexes are chosen to safeguard echoes—fragments of ancient knowledge too valuable to destroy but too dangerous to use. Forbidden to speak lest she accidentally release her echo, codex Delta lives a lonely life. Still, she knows she must obey the wardens’ strict rules to keep her home safe from the vicious beasts, heretical Scrappers, and toxic blood storms that lurk beyond the city walls.
But when Delta breaks her vows to help a young girl escape a blood storm, she begins to have strange dreams, which lead her to question everything she knows to be true about herself and her city. To find answers, Delta must journey to the one place she most fears: the wasteland beyond the walls of Danak-Tol.
Together with her small but feisty mechanical companion Flick, Delta dares the perilous ruins of a long-abandoned skyship, the gullet of a ravenous sphincter worm, and even befriends a young Scrapper named Drii. But all these adventures only lead to more questions. What is the true danger that threatens her entire planet—is it really her echo, or is it the silence that has imprisoned the truth for so long?
288 pages, Hardcover
Published April 14, 2026
About the author
Deva Fagan
10 books214 followersI write fantasy and science fiction for readers of all ages. I live in Maine with my husband and our dog. When I'm not writing I spend my time reading, playing video games, doing geometry, and drinking copious amounts of tea.
NOTE: My comments on books I've read are not meant to be critical reviews, but are just my own reactions. I don't generally use stars, but I do occasionally mark a book with five stars if it's one that feels like it will become a long-term favorite, because it's exactly my sort of book, and caters to my specific tastes as a reader. There are plenty of books I read and really admire that are clearly excellent books, but which are not so exactly "for me" that I give them five stars. I will unabashedly stop reading books I really don't care for, so if a book is on my read list at all it means I liked it enough to finish it.
NOTE: My comments on books I've read are not meant to be critical reviews, but are just my own reactions. I don't generally use stars, but I do occasionally mark a book with five stars if it's one that feels like it will become a long-term favorite, because it's exactly my sort of book, and caters to my specific tastes as a reader. There are plenty of books I read and really admire that are clearly excellent books, but which are not so exactly "for me" that I give them five stars. I will unabashedly stop reading books I really don't care for, so if a book is on my read list at all it means I liked it enough to finish it.
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Displaying 1 - 30 of 31 reviews
April 25, 2026
An engaging sci-fi dystopian fantasy set in a world that has been destroyed and ravaged by a fungi-like infestation.
Delta is one of the keepers of the codices, a group of children that keeps the knowledge of their ancient founders within themselves lead very solitary lives where they're not allowed to interact with anyone else or even allowed to speak.
But when a series of mishaps and circumstances occur, Delta finds herself thrown in the middle of an opposition political struggle, she learns of deception, manipulation, lies and hidden truths of what the world was before and why it is the way it is now.
She ends up in an unwanted adventure with a group of other people in search of a way to end the infestation.
The ending was a little bittersweet with the outcome a little somewhat disheartening and especially the tragic tale of the founder whose memories Delta is the keeper of.
The voice narration by PJ Morgan was enjoyable to listen to with an easy pacing while the different voices were done well with the varying nuances and intonations.
Overall quite entertaining!
I received a free audiobook from Netgalley for evaluation purposes.
Delta is one of the keepers of the codices, a group of children that keeps the knowledge of their ancient founders within themselves lead very solitary lives where they're not allowed to interact with anyone else or even allowed to speak.
But when a series of mishaps and circumstances occur, Delta finds herself thrown in the middle of an opposition political struggle, she learns of deception, manipulation, lies and hidden truths of what the world was before and why it is the way it is now.
She ends up in an unwanted adventure with a group of other people in search of a way to end the infestation.
The ending was a little bittersweet with the outcome a little somewhat disheartening and especially the tragic tale of the founder whose memories Delta is the keeper of.
The voice narration by PJ Morgan was enjoyable to listen to with an easy pacing while the different voices were done well with the varying nuances and intonations.
Overall quite entertaining!
I received a free audiobook from Netgalley for evaluation purposes.
Read
December 16, 2025My eighth middle grade novel will be out in April of 2026! The beautiful cover art is by James Firnhaber (https://www.jamesfirnhaber.com/ ).
The elements of this story have been with me for a long time, but only just came together a few years ago. I think my dedication for this book captures what it means to me:
To everyone raising their voice and speaking the truth, even when the world wants lies.
The elements of this story have been with me for a long time, but only just came together a few years ago. I think my dedication for this book captures what it means to me:
To everyone raising their voice and speaking the truth, even when the world wants lies.
April 14, 2026
The Delta Codex by Deva Fagan is a vivid and imaginative middle grade sci-fi fantasy that slowly draws you into its layered and intriguing world. Set in the city of Danak-Tol, the story follows Delta, a girl chosen as a “codex,” one of the few entrusted with holding fragments of ancient and potentially dangerous knowledge within her mind. To protect others, she must remain silent, living under strict rules meant to keep both her and the city safe from the threats that loom beyond its walls. When Delta breaks that silence to help someone in need, her understanding of the world begins to shift, setting her on a journey that challenges everything she has been taught.
One of the highlights for me was the worldbuilding. The story does not overwhelm you with information all at once. Instead, the setting unfolds naturally alongside Delta’s own discoveries, which made exploring it feel immersive and rewarding.
I also really enjoyed experiencing this as an audiobook. The narration by P. J. Morgan stood out, especially in the way they handled a wide range of character voices that felt distinct and fitting.
Delta’s small robotic companion added a lot of charm, bringing moments of lightness to balance the tension of the story. As the plot progressed, particularly in the final third, I found myself increasingly invested. I was fully drawn into Delta’s journey and genuinely rooting for her as the stakes grew higher.
I’m grateful to NetGalley and Dreamscape Media for the opportunity to listen to this book in advance and share my thoughts.
One of the highlights for me was the worldbuilding. The story does not overwhelm you with information all at once. Instead, the setting unfolds naturally alongside Delta’s own discoveries, which made exploring it feel immersive and rewarding.
I also really enjoyed experiencing this as an audiobook. The narration by P. J. Morgan stood out, especially in the way they handled a wide range of character voices that felt distinct and fitting.
Delta’s small robotic companion added a lot of charm, bringing moments of lightness to balance the tension of the story. As the plot progressed, particularly in the final third, I found myself increasingly invested. I was fully drawn into Delta’s journey and genuinely rooting for her as the stakes grew higher.
I’m grateful to NetGalley and Dreamscape Media for the opportunity to listen to this book in advance and share my thoughts.
April 25, 2026
3.7★
Now this was a very fun read: the world is so immersive and rich, I think it's the most outstanding aspect of this novel. The characters took their sweet time to evolve, speeding up in the third act, which didn't bother me at all, but in audiobook form, it was hard to gauge how long that was. My biggest concern, which isn't really a concern, is the age rating. This is totally in the upper side of middle-grade, I'd say, for kids 12 to 14, dealing with subjects such as religion and emotional grooming. The ecological side was well treated, with simple explanations (maybe too simple if we're targeting the upper age range, but easy to brush through). I would have loved it if the main character had her development sooner, most of the book giving into silence and almost a meek attitude that I'd find kids difficult to see themselves reflected in (some will, but I fell its a smaller demographic). I really appreciate characters using they/them pronouns too!! So refreshing to see characters with disabilities, too, from illness to selective mutism (I'm gonna treat a vow of silence as selective mutism here).
I feel this is great to initiate kids into the dystopia genre, very entertaining and with such important matters.
Now this was a very fun read: the world is so immersive and rich, I think it's the most outstanding aspect of this novel. The characters took their sweet time to evolve, speeding up in the third act, which didn't bother me at all, but in audiobook form, it was hard to gauge how long that was. My biggest concern, which isn't really a concern, is the age rating. This is totally in the upper side of middle-grade, I'd say, for kids 12 to 14, dealing with subjects such as religion and emotional grooming. The ecological side was well treated, with simple explanations (maybe too simple if we're targeting the upper age range, but easy to brush through). I would have loved it if the main character had her development sooner, most of the book giving into silence and almost a meek attitude that I'd find kids difficult to see themselves reflected in (some will, but I fell its a smaller demographic). I really appreciate characters using they/them pronouns too!! So refreshing to see characters with disabilities, too, from illness to selective mutism (I'm gonna treat a vow of silence as selective mutism here).
I feel this is great to initiate kids into the dystopia genre, very entertaining and with such important matters.
Review of advance copy received from NetGalley
Thank you NetGalley for providing me with this audiobook ARC!
At around 70% I thought this book was going to be a part 1 with a massive cliffhanger and thankfully, it wasn't. Because I would NOT have had the patience to wait for a second instalment. I give this book 4,5 stars, rounded up to 5, because I finished this audiobook in 2 days and I don't usually do that. It gripped me THAT much.
The book starts off immediately interesting: codexes (children) that have 'echoes' (memories). The Codexes live in a vault, sheltered from the world and even from each other: they are to be silent, as there is 'safety in silence'. This obviously creates a very lonely existence and we learn about how Delta wants to desperately connect with others. She only has 1 friend: Flick, who is a little monk (robot) in the shape of a flying needle. Flick was very cute, lovely and whimsical sidekick.
The Codexes are here to protect Danak-Tol, but they are stripped of their identity, are not allowed to talk or socialise (for their own protection though) and they are basically seen as pets at best, as objects at worst. So from the start, it's clear that things are not what they seem: Delta casually mentioned something and I immediately went "oh no that's bad". I was right, it is quite dystopian after all. I found some more elements to be a bit predictable, but was pleasantly surprised at others, especially for a middle grade book. For a middle grade book, I thought it dealt with some heavier themes, like environmentalism, propaganda and the misuse of power, but it was done quite well in my opinion and there wasn't a point I went "oeh that's too far for a kids book". I do have to say that the characters were quite black and white, in a good and evil kind of way. There was very little redemption possible for the antagonists, and the protagonists were mostly good.
When Delta explores the wasteland, things start to become even more interesting. The contrast between the high tech city and the low tech (but high flora and fauna) wasteland is described vividly. This world is rich, so vibrant, so interesting (if there would be a second instalment, I would buy it immediately, because I would love to explore this world more). There are some unique animals, vaguely based on earth animals, which are wonderful for the imagination. The bloom did make me think of the toxic stuff in the game Horizon Forbidden West (which I love, no critique there).
As Delta doesn't speak, as it is forbidden, we mostly rely on her inner voice and very little dialogue. Her inner voice comes through quite impressively. And I love how during the book, she finds her own voice and place in this world. And P.J. Morgan is the perfect voice to narrate Delta, so good choice, Dreamscape Media. It suited Delta really well and they also managed to convey the other characters very distinctively. I just loved listening to this narration.
The Catalog was so funny. After the first quote, I was sold on his personality, and he just kept coming up with more fun things to say. I also enjoyed the references to old world stories that Delta casually mentioned. I didn't know all of them, but I'm kind of hoping that is because they're either too old for me, published "in the future" (as if that story hasn't been written yet) or from not a Western culture. It was still fun to catch that it was a reference, even if I didn't know what it was to.
The ending though? Perfect. I won't give any spoilers, but it was everything I wanted. It fitted so well!
At around 70% I thought this book was going to be a part 1 with a massive cliffhanger and thankfully, it wasn't. Because I would NOT have had the patience to wait for a second instalment. I give this book 4,5 stars, rounded up to 5, because I finished this audiobook in 2 days and I don't usually do that. It gripped me THAT much.
The book starts off immediately interesting: codexes (children) that have 'echoes' (memories). The Codexes live in a vault, sheltered from the world and even from each other: they are to be silent, as there is 'safety in silence'. This obviously creates a very lonely existence and we learn about how Delta wants to desperately connect with others. She only has 1 friend: Flick, who is a little monk (robot) in the shape of a flying needle. Flick was very cute, lovely and whimsical sidekick.
The Codexes are here to protect Danak-Tol, but they are stripped of their identity, are not allowed to talk or socialise (for their own protection though) and they are basically seen as pets at best, as objects at worst. So from the start, it's clear that things are not what they seem: Delta casually mentioned something and I immediately went "oh no that's bad". I was right, it is quite dystopian after all. I found some more elements to be a bit predictable, but was pleasantly surprised at others, especially for a middle grade book. For a middle grade book, I thought it dealt with some heavier themes, like environmentalism, propaganda and the misuse of power, but it was done quite well in my opinion and there wasn't a point I went "oeh that's too far for a kids book". I do have to say that the characters were quite black and white, in a good and evil kind of way. There was very little redemption possible for the antagonists, and the protagonists were mostly good.
When Delta explores the wasteland, things start to become even more interesting. The contrast between the high tech city and the low tech (but high flora and fauna) wasteland is described vividly. This world is rich, so vibrant, so interesting (if there would be a second instalment, I would buy it immediately, because I would love to explore this world more). There are some unique animals, vaguely based on earth animals, which are wonderful for the imagination. The bloom did make me think of the toxic stuff in the game Horizon Forbidden West (which I love, no critique there).
As Delta doesn't speak, as it is forbidden, we mostly rely on her inner voice and very little dialogue. Her inner voice comes through quite impressively. And I love how during the book, she finds her own voice and place in this world. And P.J. Morgan is the perfect voice to narrate Delta, so good choice, Dreamscape Media. It suited Delta really well and they also managed to convey the other characters very distinctively. I just loved listening to this narration.
The Catalog was so funny. After the first quote, I was sold on his personality, and he just kept coming up with more fun things to say. I also enjoyed the references to old world stories that Delta casually mentioned. I didn't know all of them, but I'm kind of hoping that is because they're either too old for me, published "in the future" (as if that story hasn't been written yet) or from not a Western culture. It was still fun to catch that it was a reference, even if I didn't know what it was to.
The ending though? Perfect. I won't give any spoilers, but it was everything I wanted. It fitted so well!
May 7, 2026
Review of advance copy received from NetGalley.
4 ⭐️
Delta doesn’t know her real name. She doesn’t remember her past, or her family, though she’s told they’re out there waiting for her; waiting for her to complete her duty as a Codex, a keeper of sacred — and potentially dangerous — knowledge of her world’s beginnings. Unable to speak without risking the turmoil this knowledge may bring upon her people, she dutifully goes about her work until the choice between what she feels is right and what she’s been taught to protect catapults her into unknown territory.
This book is a fast-paced, action-packed adventure perfect for middle grade dystopian sci-fi readers. It does lean heavily on the main character’s mostly silent exposition in the first third of the book, which made the very beginning both a little slow and like drinking from a fire hose, but once more character interactions were introduced it started to move and flow more easily.
It was crazy to me how this entire story happens within what I’m assuming to be approximately a week (or less), & there is so much squeezed into less than 8 hours of book. This could easily have been at least a duology if the world-building and story had been expanded (that is to say, slowed down with even more detail) but I can also appreciate that it was kept as a single novel for middle grade readability.
I ended up appreciating Delta’s inner monologue, particularly moments when she defined words that she recognized that could be familiar but difficult to understand on their own to younger readers. Delta’s story is your typical reluctant hero turned rebel leader/symbol, and don’t forget to add in a dash of found family.
The cast of characters was diverse, with various backgrounds allowing us to learn more about the world through Delta’s eyes and our knowledge and understanding growing with hers. With the story being so fast-paced, you still get a decent picture of all the main side characters’ personalities, just enough to be able to fill in the gaps for yourself and to experience the amount of character growth there was time for.
The plot dealt with some pretty heavy topics beautifully, from climate change and pollution to emotional grooming and challenging authority to censorship and religious constructs. P. J. Morgan was engaging to listen to, and I always enjoy a variety of voices to differentiate between characters.
All in all, I can see myself recommending this to my future middle school kiddos to stoke that love-of-dystopian-sci-fi flame, and I’m looking forward to seeing what else Deva Fagan creates.
P. S. - I’m still laughing at a run-in with a creature called a “Sphincter” and I think that says a lot about the target audience. Marvelous!
Thank you to NetGalley, Dreamscape Audio, and Atheneum Books for this advance audiobook in exchange for my honest feedback.
4 ⭐️
Delta doesn’t know her real name. She doesn’t remember her past, or her family, though she’s told they’re out there waiting for her; waiting for her to complete her duty as a Codex, a keeper of sacred — and potentially dangerous — knowledge of her world’s beginnings. Unable to speak without risking the turmoil this knowledge may bring upon her people, she dutifully goes about her work until the choice between what she feels is right and what she’s been taught to protect catapults her into unknown territory.
This book is a fast-paced, action-packed adventure perfect for middle grade dystopian sci-fi readers. It does lean heavily on the main character’s mostly silent exposition in the first third of the book, which made the very beginning both a little slow and like drinking from a fire hose, but once more character interactions were introduced it started to move and flow more easily.
It was crazy to me how this entire story happens within what I’m assuming to be approximately a week (or less), & there is so much squeezed into less than 8 hours of book. This could easily have been at least a duology if the world-building and story had been expanded (that is to say, slowed down with even more detail) but I can also appreciate that it was kept as a single novel for middle grade readability.
I ended up appreciating Delta’s inner monologue, particularly moments when she defined words that she recognized that could be familiar but difficult to understand on their own to younger readers. Delta’s story is your typical reluctant hero turned rebel leader/symbol, and don’t forget to add in a dash of found family.
The cast of characters was diverse, with various backgrounds allowing us to learn more about the world through Delta’s eyes and our knowledge and understanding growing with hers. With the story being so fast-paced, you still get a decent picture of all the main side characters’ personalities, just enough to be able to fill in the gaps for yourself and to experience the amount of character growth there was time for.
The plot dealt with some pretty heavy topics beautifully, from climate change and pollution to emotional grooming and challenging authority to censorship and religious constructs. P. J. Morgan was engaging to listen to, and I always enjoy a variety of voices to differentiate between characters.
All in all, I can see myself recommending this to my future middle school kiddos to stoke that love-of-dystopian-sci-fi flame, and I’m looking forward to seeing what else Deva Fagan creates.
P. S. - I’m still laughing at a run-in with a creature called a “Sphincter” and I think that says a lot about the target audience. Marvelous!
Thank you to NetGalley, Dreamscape Audio, and Atheneum Books for this advance audiobook in exchange for my honest feedback.
Review of advance copy received from Netgalley
3.75 Stars Rounded Up
The Delta Codex by Deva Fagan delivers an imaginative sci-fi/fantasy that explores environmental issues with an emotional coming-of-age story. Set in the deceptive utopian city of Danak-Tol, the story draws you in with the intriguing premise of : children called codexes being chosen to be “honored” vessels for dangerous “echoes” of ancient knowledge.
Delta (main character) is a native and compliant protagonist whose loneliness and virtuousness shape the emotional core of the story. Her vow of silence creates a powerful sense of isolation, and the narrative does an excellent job of conveying her inner world without relying on spoken dialogue. As she begins to question the dynamics and leadership within the system she’s always trusted. She internally struggles between conforming to societal norms/laws and self exploration all within an increasingly dangerous environment.
The worldbuilding is one of the most interesting components within the story, because it’s imaginative and innovative filled with striking elements such as toxic blood storms, mechanical companions, strange wasteland creatures, and ruins of lost technologies. Each new setting feels treacherous and alive, reinforcing the sense that this planet holds far more secrets than its citizens are allowed to know.
One of the book’s greatest strengths is how it explores its central theme: the cost of restricted knowledge. Through Delta’s journey, the story asks thoughtful questions about truth, power, and whether knowledge itself is truly dangerous—or if control of it is the greater threat. Additionally, the relationships Delta forms along the way—especially with Flick—added much needed warmth and balance to Delta’s naivety and the darker elements of the story. Personally, one drawback was the pacing which occasionally slowed during exposition-heavy sections especially detailed environments, but the mystery surrounding the echoes and the world itself kept me wanting to read more.
Overall, The Delta Codex is a creative and thought-provoking debut that will appeal to readers who enjoy imaginative sci-fi worlds, heavily focused character journeys, and layered mysteries. It’s a story about belonging,, autonomy and the courage of seeking truth even when silence feels safer.
**this story may be more suitable for children on the higher end of the age range for middle grade**
A special thanks to Simon & Schuster Children’s Publishing, and NetGalley for the Advanced Reader’s Copy for review. My reviews always reflect my honest thoughts and feelings.
The Delta Codex by Deva Fagan delivers an imaginative sci-fi/fantasy that explores environmental issues with an emotional coming-of-age story. Set in the deceptive utopian city of Danak-Tol, the story draws you in with the intriguing premise of : children called codexes being chosen to be “honored” vessels for dangerous “echoes” of ancient knowledge.
Delta (main character) is a native and compliant protagonist whose loneliness and virtuousness shape the emotional core of the story. Her vow of silence creates a powerful sense of isolation, and the narrative does an excellent job of conveying her inner world without relying on spoken dialogue. As she begins to question the dynamics and leadership within the system she’s always trusted. She internally struggles between conforming to societal norms/laws and self exploration all within an increasingly dangerous environment.
The worldbuilding is one of the most interesting components within the story, because it’s imaginative and innovative filled with striking elements such as toxic blood storms, mechanical companions, strange wasteland creatures, and ruins of lost technologies. Each new setting feels treacherous and alive, reinforcing the sense that this planet holds far more secrets than its citizens are allowed to know.
One of the book’s greatest strengths is how it explores its central theme: the cost of restricted knowledge. Through Delta’s journey, the story asks thoughtful questions about truth, power, and whether knowledge itself is truly dangerous—or if control of it is the greater threat. Additionally, the relationships Delta forms along the way—especially with Flick—added much needed warmth and balance to Delta’s naivety and the darker elements of the story. Personally, one drawback was the pacing which occasionally slowed during exposition-heavy sections especially detailed environments, but the mystery surrounding the echoes and the world itself kept me wanting to read more.
Overall, The Delta Codex is a creative and thought-provoking debut that will appeal to readers who enjoy imaginative sci-fi worlds, heavily focused character journeys, and layered mysteries. It’s a story about belonging,, autonomy and the courage of seeking truth even when silence feels safer.
**this story may be more suitable for children on the higher end of the age range for middle grade**
A special thanks to Simon & Schuster Children’s Publishing, and NetGalley for the Advanced Reader’s Copy for review. My reviews always reflect my honest thoughts and feelings.
May 4, 2026
This middle-grade sci-fi book was engaging and thoughtful. The Delta Codex follows 12-year old protagonist Delta who is assigned to guard a memory stored in her body. She doesn’t know who the memory belongs to or what it is, but she is told it is dangerous. There is so much tension throughout this book, and I think children will enjoy its twists and turns.
There is also a wonderful message about self-determination for young people. While Delta’s life in an underground vault does not seem to make her particularly happy and deprives her of familial relationships and friendships, she believes strongly in her role as a protector of the wonderful city that benefits from her work. Throughout the book, she has to painfully realize that her sacrifice may not be for a purpose that she believes in. However, by meeting new people and experiencing other ways of life, Delta is able to choose a better outcome for herself.
Also, if the idea of child sacrifices fueling utopias seems familiar, there will be a lot of other popular sci-fi references for you to notice as well! I wonder if younger teens might also enjoy this book, it is very dense in themes and politically relevant. While The Delta Codex probably won’t feel too original for adults, I can imagine deeply connecting to it if I was younger, and less trope-conscious.
Thank you to Simon and Schuster Children's Publishing, Dreamscape Media, & Netgalley for the ebook and eAudiobook!
Notes specific to the audiobook version: I really liked the narration by P.J. Morgan. This book has a lot of inner turmoil, and I think they portrayed Delta’s mixed emotions in a way that would be clear to children.
There is also a wonderful message about self-determination for young people. While Delta’s life in an underground vault does not seem to make her particularly happy and deprives her of familial relationships and friendships, she believes strongly in her role as a protector of the wonderful city that benefits from her work. Throughout the book, she has to painfully realize that her sacrifice may not be for a purpose that she believes in. However, by meeting new people and experiencing other ways of life, Delta is able to choose a better outcome for herself.
Also, if the idea of child sacrifices fueling utopias seems familiar, there will be a lot of other popular sci-fi references for you to notice as well! I wonder if younger teens might also enjoy this book, it is very dense in themes and politically relevant. While The Delta Codex probably won’t feel too original for adults, I can imagine deeply connecting to it if I was younger, and less trope-conscious.
Thank you to Simon and Schuster Children's Publishing, Dreamscape Media, & Netgalley for the ebook and eAudiobook!
Notes specific to the audiobook version: I really liked the narration by P.J. Morgan. This book has a lot of inner turmoil, and I think they portrayed Delta’s mixed emotions in a way that would be clear to children.
Review of advance copy received from NetGalley
Know what you are getting. This book has elements of post apocalyptic, sci-fi and fantasy, and young adult non-romance. It is a standalone novel, not a part of a series.
This book has multiple themes, including what industrialization without a single care for the environment does, how being without a voice to isolates people, friendship and what it means to be a friend, and good versus evil/arrogant. I love that there is not a single bit of romance in the book.
The dialogue in this book does seem a little advanced for the ages of the characters presented. That is normally to be expected to create a good flow. I feel like the dialogue was fairly tight and well written. The world building was quite enjoyable and had similar themes of other silo style post apocalyptic cities.
I did not feel like themes were preachy. The author took a very simple balanced approach to the subject matter being written.
The only con I have about this book is that there did not seem to be a very good gray area between good and evil. The good people were good. The bad people were very bad and or arrogant.
The narration was absolutely fantastic with good pacing and good inflections, and it was easy to understand who was speaking based on the voice.
Story: 4/5
This book has multiple themes, including what industrialization without a single care for the environment does, how being without a voice to isolates people, friendship and what it means to be a friend, and good versus evil/arrogant. I love that there is not a single bit of romance in the book.
The dialogue in this book does seem a little advanced for the ages of the characters presented. That is normally to be expected to create a good flow. I feel like the dialogue was fairly tight and well written. The world building was quite enjoyable and had similar themes of other silo style post apocalyptic cities.
I did not feel like themes were preachy. The author took a very simple balanced approach to the subject matter being written.
The only con I have about this book is that there did not seem to be a very good gray area between good and evil. The good people were good. The bad people were very bad and or arrogant.
The narration was absolutely fantastic with good pacing and good inflections, and it was easy to understand who was speaking based on the voice.
Story: 4/5
May 4, 2026
So glad to have a new sci fi title for younger readers that gracefully combines real life issues and the fantastical. I think middle school me would have eaten this up and probably drawn fan art for it too. The exploration of flora, fauna, and tech is fun and interesting, and the cast of characters have their own complexities and appeals. I found Delta's reactions to be realistic, her navigation of trust and new friendships understandable and honest. The main kids are a unique group, learning to communicate and support one another while a lot is at stake.
I thought the narrator did a solid job of distinguishing vocal characteristics for the various adults and children. I will also say that Delta starts out with a sort of perpetual breathy concern which I found distracting at first. It makes sense for her character and the uncertainty she is facing, but I was glad when her growing confidence starts to be reflected more. In hindsight, pretty fitting for a character raised to believe there is safety in silence.
This is a great option for readers passionate about environmental concerns, themes of friendship, found family, and self discovery.
This is a review of the audiobook. Many thanks to NetGalley and Dreamscape Media for the advanced listening copy.
I thought the narrator did a solid job of distinguishing vocal characteristics for the various adults and children. I will also say that Delta starts out with a sort of perpetual breathy concern which I found distracting at first. It makes sense for her character and the uncertainty she is facing, but I was glad when her growing confidence starts to be reflected more. In hindsight, pretty fitting for a character raised to believe there is safety in silence.
This is a great option for readers passionate about environmental concerns, themes of friendship, found family, and self discovery.
This is a review of the audiobook. Many thanks to NetGalley and Dreamscape Media for the advanced listening copy.
Review of advance copy received from Netgalley
3.5 stars, rounded up because it's an adventure that will be engaging for the target age audience (middle-grades readers). But that's also one of my concerns: this book is clearly written for middle-grades readers, but the content is pretty dark and heavy for that age group, imo (but not really straying into YA-specific themes). I think it would be a good fit for older middle-grades readers, but maybe if they know what to expect.
The overarching theme of anti-industrialization does get a little preachy, though not as bad as I've seen other places.
The writing style also didn't really work for me. The book is well written, but by necessity (due to world-building) there is a lot of description and very little dialogue, especially in the first half. For me, this makes the story drag some and feels like reading a narration of a story, rather than experiencing it. It's not quite as bad as some other books I've read (looking at you, Earthsea), but I personally didn't love it. Not sure younger readers will have any problem with it, though.
Thank you to the publisher and NetGalley for the digital ARC.
The overarching theme of anti-industrialization does get a little preachy, though not as bad as I've seen other places.
The writing style also didn't really work for me. The book is well written, but by necessity (due to world-building) there is a lot of description and very little dialogue, especially in the first half. For me, this makes the story drag some and feels like reading a narration of a story, rather than experiencing it. It's not quite as bad as some other books I've read (looking at you, Earthsea), but I personally didn't love it. Not sure younger readers will have any problem with it, though.
Thank you to the publisher and NetGalley for the digital ARC.
April 23, 2026
The Delta Codex Audiobook: 4.5⭐️
The Delta Codex by Deva Fagan was a really interesting science fiction story. The story follows Delta, a twelve years old girl who was chosen to be a Codex. The world she lives in is endangered by a blood storm. The codexes are there to protect the city of Danak-Tol and its people from it. However, as we start following Delta’s story, we quickly understand that what she has been told and what she believed in might not be the truth. The Delta Codex story follows her in a mission to save Danak-Tol, its people and the waste land from the blood storm and those who endanger this new world.
I really enjoyed this audiobook. The narration was beautiful and the narrator had a good pace. It was easy to follow and to get into the story. The story itself was good as well. It is easy to imagine the world and the characters are interesting. It is perfect for young teens who are getting into science fiction, but it is also enjoyable for an adult as it is not childish and the world created by the author is an interesting one to discover. I would give the overall story a 4.5 stars on 5.
The Delta Codex by Deva Fagan was a really interesting science fiction story. The story follows Delta, a twelve years old girl who was chosen to be a Codex. The world she lives in is endangered by a blood storm. The codexes are there to protect the city of Danak-Tol and its people from it. However, as we start following Delta’s story, we quickly understand that what she has been told and what she believed in might not be the truth. The Delta Codex story follows her in a mission to save Danak-Tol, its people and the waste land from the blood storm and those who endanger this new world.
I really enjoyed this audiobook. The narration was beautiful and the narrator had a good pace. It was easy to follow and to get into the story. The story itself was good as well. It is easy to imagine the world and the characters are interesting. It is perfect for young teens who are getting into science fiction, but it is also enjoyable for an adult as it is not childish and the world created by the author is an interesting one to discover. I would give the overall story a 4.5 stars on 5.
May 8, 2026
Delta lives in the Vault of Echoes in the city of Danak-Tol where she is a living repository of the Founders, who two centuries again fled a dying planet for a new one, memories. There are two rules she must foloow - never speak, less she awaken her echo and never been seen. While trying to fix a mechanical issue with her munk friend, Flick, a mechanical bird, a bloodstorm threatens a little girl and her father and Delta breaks both rules to try and save them. She only saves Zora and then her life takes a turn for the worst. Invited to a special party with her protector, Wardn Veela, to meet Governor Rast, Jyn and Kesi, twins, tell Delta truths that turn her entire life into lies. Forced outside into the wasteland to survive, Delta must face harrowin adventures, find her voice and bravery, and turn to friends she makes along the way to try to save Danka-Tol and everything she has always held dear. Masterful world building. Amazing character arcs for not just Delta but her friends. Humor intermingles with the deperation and emotional tags of the adventure that never let's up as Delta goes from issue to the next. A beautifully written dystopian scince-fiction thriller.
Review of advance copy received from Netgalley
4☆ | this was a wonderful and fun book. I was able to guess a few of the things that later ended up happening but that didn't make it any less enjoyable for me.
𝑻𝒉𝒐𝒖𝒈𝒉𝒕𝒔:
I felt that the story was well thought out and executed and while I was
I loved the characters and especially loved seeing Delta's growth throughout the story, how she started to think for herself and not let how she was raised stop her from doing what she felt was right.
The world was also incredibly intriguing and I loved what we saw of it.
I got the audiobook for this and I really enjoyed the narration. Was really easy to understand and I could clearly tell which character was speaking when they did.
𝑶𝒗𝒆𝒓𝒂𝒍𝒍:
I know this is a standalone book but I would love to see more of the world, both before and after the events of this one. And this is a middle grade book though doesn't feel overly childish or anything, and I felt that it's a good book even for older readers.
Thank you to NetGalley and the publishers for allowing me to have an advanced copy in exchange for an honest review!
𝑻𝒉𝒐𝒖𝒈𝒉𝒕𝒔:
I felt that the story was well thought out and executed and while I was
I loved the characters and especially loved seeing Delta's growth throughout the story, how she started to think for herself and not let how she was raised stop her from doing what she felt was right.
The world was also incredibly intriguing and I loved what we saw of it.
I got the audiobook for this and I really enjoyed the narration. Was really easy to understand and I could clearly tell which character was speaking when they did.
𝑶𝒗𝒆𝒓𝒂𝒍𝒍:
I know this is a standalone book but I would love to see more of the world, both before and after the events of this one. And this is a middle grade book though doesn't feel overly childish or anything, and I felt that it's a good book even for older readers.
Thank you to NetGalley and the publishers for allowing me to have an advanced copy in exchange for an honest review!
Review of advance copy received from Netgalley
This hyper-ambitious middle grade fantasy has stellar world-building, deeply poignant messages about the climate crisis and misinformation, and a phenomenal heroine in Delta. As she learns more about her life and as she and her ragtag crew take on corrupt politicians and impending storms, it is easy to root for Delta and feel inspired to do better in our world.
While this book is written for middle grade readers, I would recommend it more for middle school than upper elementary. The world-building is VERY complex, and I found myself getting confused at times. There are also some very deep and complex themes here, and it would benefit readers to either have more background in social studies or have an adult read with them. There is so much goodness here that I would not want readers to miss. I highlighted several lines that I want to keep for the future!
Thank you to NetGalley and Altheneum Books for Young Readers for an eARC in exchange for my honest review.
While this book is written for middle grade readers, I would recommend it more for middle school than upper elementary. The world-building is VERY complex, and I found myself getting confused at times. There are also some very deep and complex themes here, and it would benefit readers to either have more background in social studies or have an adult read with them. There is so much goodness here that I would not want readers to miss. I highlighted several lines that I want to keep for the future!
Thank you to NetGalley and Altheneum Books for Young Readers for an eARC in exchange for my honest review.
Review of advance copy received from Netgalley
Beautiful. I would give this 6 stars if I could.
The character development of the MC from the first chapter to the last is mind boggling. The world building? Even more so. This is one of the most unique worlds I've ever read. It was intricate and detailed and purposeful.
I loved all the characters except a select few that I wanted to toss from the book and tell them what for, but they weren't meant to be hated. They were meant to be seen as brainwashed by the corrupt government and absolute fear of a dying system.
The ending was perfect for the MC and for the world. When you read it, you'll understand because I can't spoil it! But for the storyline? Perfection.
Thank you to NetGalley for the E-Arc in exchange for an honest review.
The character development of the MC from the first chapter to the last is mind boggling. The world building? Even more so. This is one of the most unique worlds I've ever read. It was intricate and detailed and purposeful.
I loved all the characters except a select few that I wanted to toss from the book and tell them what for, but they weren't meant to be hated. They were meant to be seen as brainwashed by the corrupt government and absolute fear of a dying system.
The ending was perfect for the MC and for the world. When you read it, you'll understand because I can't spoil it! But for the storyline? Perfection.
Thank you to NetGalley for the E-Arc in exchange for an honest review.
Review of advance copy received from Netgalley
This new world views humans as an invasive species, but is the flora really our enemy?
An amazing future dystopian middle-grade adventure with great character development. It follows a child carrying so much knowledge she is afraid to speak, moving from silence and submission to rebellion, action, and bravery on behalf of humankind.
I loved the little sidekick and also the Catalog. He is the best, always speaking in super fun, well-known quotes from history, pop culture, and more. Hearing him say, 'I tell you what I want, what I really, really want' made me instantly smile. I listened to the audiobook on NetGalley and it is amazing. I will definitely grab a physical copy when possible because the cover is so beautiful I want to display it on my wall like a painting.
An amazing future dystopian middle-grade adventure with great character development. It follows a child carrying so much knowledge she is afraid to speak, moving from silence and submission to rebellion, action, and bravery on behalf of humankind.
I loved the little sidekick and also the Catalog. He is the best, always speaking in super fun, well-known quotes from history, pop culture, and more. Hearing him say, 'I tell you what I want, what I really, really want' made me instantly smile. I listened to the audiobook on NetGalley and it is amazing. I will definitely grab a physical copy when possible because the cover is so beautiful I want to display it on my wall like a painting.
May 3, 2026
The Delta Codex was a refreshing change of pace. It follows a young girl known as Delta on her journey to learn the truth of herself and the world around her. We find Delta as a girl who is wholeheartedly dedicated to keeping her home safe, even if that means blindly trusting the wardens around her, that is, until she starts getting curious and seeking answers for herself.
The beginning was a bit slow while world building, but once you get through the first 25%-30% it is one thing after another and the story really plummets you into the action. The narrator did a wonderful job of bringing life to each of the characters in a way that was exciting but still appropriately reflected the youth of the characters.
The beginning was a bit slow while world building, but once you get through the first 25%-30% it is one thing after another and the story really plummets you into the action. The narrator did a wonderful job of bringing life to each of the characters in a way that was exciting but still appropriately reflected the youth of the characters.
April 16, 2026
Review of advanced copy received from Netgalley
3.75 rounded up. The Delta Codex is an imaginative and inspiring Middle-Grade novel that challenges the reader to reflect on what it means to think for yourself and what lengths do you go to do the right thing. Right off the bat I noticed the lovely warmth to Fagan’s writing and how immersive Danak-Tol and Delta’s world is. This story was full of funny, emotional, and inspiring moments readers of all ages will enjoy. The audiobook’s narrator gave a stellar performance and portrayed Delta’s voice and empathy wonderfully. I would love to read more from this world in the future.
3.75 rounded up. The Delta Codex is an imaginative and inspiring Middle-Grade novel that challenges the reader to reflect on what it means to think for yourself and what lengths do you go to do the right thing. Right off the bat I noticed the lovely warmth to Fagan’s writing and how immersive Danak-Tol and Delta’s world is. This story was full of funny, emotional, and inspiring moments readers of all ages will enjoy. The audiobook’s narrator gave a stellar performance and portrayed Delta’s voice and empathy wonderfully. I would love to read more from this world in the future.
October 22, 2025
ARC Copy...Actually on heavy side for middle grade which is good and even by the premise I really wanted to know what is the big secret is! Themes of ecology and censorship. It is obvious and uncomfortable to read through for a good reason that there is something wrong with Delta's world and her adult handlers , and not just the fact over how dehumanized Delta and her fellow Codexes are treated, which the codexes themselves don't seem to notice. So I was really happy once the secret was revealed cause now the heroes have to save the world before it comes crushing down literally.
April 21, 2026
I think the idea that there is no quick-fix to a problem of that scale that has grown over time, is something I really loved. Real change takes sacrifice, time and the power of friendship, of course.
I especially enjoyed how this book directly takes a look at the real climate crisis of our world. We don't have the ships to jump worlds (Mars is not an option), so we're pretty much stuck with this one. We gotta do better.
Amazing story fr.
I especially enjoyed how this book directly takes a look at the real climate crisis of our world. We don't have the ships to jump worlds (Mars is not an option), so we're pretty much stuck with this one. We gotta do better.
Amazing story fr.
This entire review has been hidden because of spoilers.
April 15, 2026
Deva Fagan is quickly becoming a must-read author for me. I absolutely loved couragous Delta and her headstrong committment to her community. It was such a joy to watch her grow as she went on adventures and made new friends. To top it all off, the joy and whimsy sprinkles throughout the story brought out regular giggles. I'll definitey be recommending this to my fantasy friends.
April 27, 2026
I would like to thank Netgalley and the publisher for providing me with an audio ARC.
This was a pretty great middle grade book. I loved the main character, Delta in this book. I loved the themes explored in this book surrounding information, environment, and religion. The world building was excellent and interesting to explore. The narrator was very engaging to listen to.
This was a pretty great middle grade book. I loved the main character, Delta in this book. I loved the themes explored in this book surrounding information, environment, and religion. The world building was excellent and interesting to explore. The narrator was very engaging to listen to.
May 4, 2026
The Delta Codex was a engaging and fast paced middle grade sci-fi dystopian adventure. This book has important messages for readers about why authorities may try to silence people and to question the information you are being given and think critically. Perfect for people who like books like The City of Ember.
Thanks to netgalley for the audio arc.
#indigoemployee
Thanks to netgalley for the audio arc.
#indigoemployee
May 6, 2026
Excellent sci fi dystopian novel that is set in a world that echoes our world today. I loved the commentary on literature, control, censorship and the power of voice. It was not at all didactic or in your face lesson centric but the message was still very clear. Well done!
Review of advance copy received from Edelweiss+
E ARC provided by Edelweiss Plus
Review of advance copy received from Author
A vividly engrossing story of terraforming gone askew, and the brave kids who fight to save their world. Excellent reading!
April 5, 2026
I received an ARC of this book from NetGalley in exchange for an honest review.
This was a MG novel with great characters and a unique storyline. I really liked it!
This was a MG novel with great characters and a unique storyline. I really liked it!
April 27, 2026
This is a mix of the giver and space, with how we preserve memory. Interesting
April 28, 2026
I've been reading some great middle grade this month. Delta is a great mc and this sci-fi world is the interesting and unique. I liked the ending and wouldn't mind reading a sequel.
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