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 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?
I 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.
My 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 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.
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!
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.
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.
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.
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!
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.
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.
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.
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.
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.
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.