The Delta Codex

by Deva Fagan

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?

Genres: Science Fiction

288 pages, Hardcover

Expected publication April 14, 2026

About the author

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.

Reviews

[Deva Fagan]

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.

[Cathy Newman · Rating 4 out of 5]

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.

[Engel Dreizehn · Rating 4 out of 5]

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.

[Ms. Yingling · Rating 3 out of 5]

E ARC provided by Edelweiss Plus