Book Review : A Letter to the Luminous Deep

I received this book for free from NetGalley in exchange for an honest review. This does not affect my opinion of the book or the content of my review.

Book Review : A Letter to the Luminous DeepA Letter to the Luminous Deep by Sylvie Cathrall
Published by Orbit on April 25th 2024
Genres: Fantasy, Romance
Pages: 432
Buy on Amazon, Barnes & Noble, or
Find on Goodreads
Source: NetGalley

Dive into the curious correspondence of Sylvie Cathrall’s delightful debut novel, A Letter to the Luminous Deep.
A beautiful discovery outside the window of her underwater home prompts the reclusive E. to begin a correspondence with renowned scholar Henerey Clel. The letters they share are filled with passion, at first for their mutual interests, and then, inevitably, for each other.
Together, they uncover a mystery from the unknown depths, destined to transform the underwater world they both equally fear and love. But by no mere coincidence, a seaquake destroys E.’s home, and she and Henerey vanish.
A year later, E.’s sister Sophy, and Henerey’s brother Vyerin, are left to solve the mystery of their siblings’ disappearances with the letters, sketches and field notes left behind. As they uncover the wondrous love their siblings shared, Sophy and Vyerin learn the key to their disappearance – and what it could mean for life as they know it.
Perfect for fans of A Marvellous Light and TJ Klune, A Letter to the Luminous Deep is a whimsical epistolary fantasy set in a mystical underwater world with mystery and heart-warming romance.

I really wanted to like A Letter to the Luminous Deep—the cover is lovely, the concept is unique, the characters are likable, and the epistolary style is immersive. This was one of my most anticipated books of the year, but unfortunately, it was very difficult for me to even reach 34% of the way through the novel, let alone push through the rest of it. And it’s not because A Letter to the Luminous Deep is poorly written or anything like that, it just moved incredibly slowly.


The story is told exclusively through letters and occasionally, through other pieces of writing, like diary entries and field journals. Readers learn that two characters, E. and Scholar Henerey Clel, who struggle to make friends due to their introverted and anxious natures, start a timid correspondence over a mysterious fish. We have access to their letters and are able to witness their mutual growing importance to each other due to their siblings, Sophy and Vyerin. The siblings are going through the correspondence of E. And Henerey in attempts to piece together what became of them, as the two disappeared from E.’s now destroyed underwater home without a trace.


I was incredibly intrigued by the mystery of their disappearance and by another puzzle A Letter to the Luminous Deep presents. Admittedly, I felt like I was following breadcrumbs of information through the woods—there were hints at the larger world, with remarks to a global, devastating event, known as The Dive, that rendered humanity forever changed. Tiny bits of information are only alluded to once every ten exchanged letters or so and the focus is truly on the humdrum of everyday life for these characters. It’s even pretty easy to forget much of the novel is taking place underwater, when one is more frequently reading about things like the broken legs of a beloved chair and whatnot. It’s not until about halfway through this 432 page book that the pace starts to pick up a little bit. I would have loved to learn more about the world of this novel, as a huge fan of BioShock, a videogame taking place in a dystopian, crumbling city built entirely under the sea, I am quite enamored with the concept of underwater life. I was excited to see what a different, healthier civilization under the waves would look like.


What little I gleaned about life in this water-based civilization was captivating. I did enjoy reading about the technology used—automaton porpoises to help researchers make it to the depths, portable habitats known as bubbles, research complexes under the sea known as the Spheres, and mail boats. Though all of these technologies were fascinating to me, they take a back seat to the daily life of E. and to that of other characters, and all descriptions of them are disappointingly vague. I felt I wasn’t given enough details to even form a clear picture of what these technologies looked like. And I never learned how they were developed or how exactly they worked. I couldn’t help but to be bummed to not know more of the nitty gritty details of this world and how it functioned and felt frustrated that the novel only scratched the surface of this information time and time again.


It was my persistent interest in these breadcrumbs involving the world and also those regarding the mystery of the characters which kept me pushing until I finished the novel. I considered DNF-ing multiple times because I was concerned that the hints weren’t ever going anywhere, and nothing eventful was ever going to happen, but I prevailed. Unfortunately, my reward was a cliffhanger, but more on that later.


Though the prose of A Letter to the Luminous Deep is lovely and the letters shared create an intimate atmosphere, it was very difficult for me to focus on their content, which were written in the same tone and voice for all of the different characters, who were sometimes from quite different walks of life or of very different ages. All characters wrote in rather formal, somewhat antiquated colloquialisms, which consists of saying things along the lines of:


Perhaps your mood has lifted even more since you responded to Scholar Clel’s letter, as I assume you have now? I can hardly count the number of times I have tried to convince you that occasional conversation with a kindred spirit can cure most ills.”


“Though I dare not say that I wish I were not a Scholar, I have felt of late a desire to escape to—to—well, somewhere else, and at present, I can think of no better elsewhere than the world you inhabit.”


This lack of variation between the letters and the writers made it difficult to discern who was writing to whom and the labels before each letter became indispensable to making this distinction. At one point, the novel offhandedly tells us that this is the speech everyone in the academic world uses, but I can’t fathom there being no other distinguishing features between the written word of such different characters, some of whom aren’t even scholars. There are no catch phrases, grammar quirks, technical jargon from different careers, or anything else distinguishing them from each other. Different fonts would have at least helped differentiate the writers, but there aren’t any used. The biggest difference we see in the letters is that one character doesn’t like to use the automated post system, which I gathered is something vaguely resembling underwater email.


Despite the notable lack of difference in the characters’ written word, something that seems quite pivotal in an epistolary novel, I did come to care for main character E.. I struggled to feel invested in other characters, as they just weren’t as compelling or sympathetic to me. E.’s younger sister, Sophy, is much more outgoing and details her own queer, slow-burn romance through her letters to her sister. This romance worked a bit better for me than the deepening bond between Henerey and E.—I think because it felt like Sophy and her love interest were on more equal footing. E., who is for all intents and purposes a shut-in due to her mental health struggles, has plenty to offer as a pen pal, but I worried for her ability to be a partner for someone actively taking part in the world.


On top of making E. such a sympathetic character,  A Letter to the Luminous Deep makes life under the ocean or Sophy’s free deep dives as part of a research team feel cozy and unthreatening. It makes the ocean feel like a wondrous place just waiting to be discovered rather than a dark, deep unfathomable abyss filled with monstrous looking creatures. However unlike other cozy fantasies, like Bookshops & Bonedust, I felt that there just wasn’t a whole of substance and that not much was actually happening. At the point of the novel that I almost stopped reading for good, the biggest thing that had happened was that E.’s brother and his fiancée had come to live with her and she found the sudden invasion and forced cohabitation deeply unpleasant. Meanwhile, Sophy and Vyerin, commented to each other on the correspondence of E. and Henerey and took note of the deepening bond between their two kindred spirit siblings, something that readers have already noticed for themselves.


Unfortunately, every time I picked up A Letter to the Luminous Deep, it felt like a losing battle against myself, as my consciousness slipped away.  It was a struggle to reign myself in enough to focus on the novel. Though I kept hoping that the mysteries or more information on the world would take center stage, they didn’t until almost the very end of the novel. To make matters worse, A Letter to the Luminous Deep then ends on a cliffhanger, leaving readers practically none the wiser about what E. and Henerey’s disappearance means for humanity. I am not 100 percent certain if I will read the next novel in the series, as I’m not sure I want to deal with the wretchedly slow pace again, but my interest in the world-building and the pervasive mystery is probably enough for me to give the series one more try.


Book Review : A Letter to the Luminous Deep - Blogging with Dragons

Posted March 8, 2024 in ARCS, Book Reviews, Fantasy

Tags: ,

6 responses to “Book Review : A Letter to the Luminous Deep

  1. I’m so sad you didn’t enjoy this more, since I have a copy and was looking forward to it. I probably won’t get to it until next month, so it will be interesting to compare notes.

  2. I’m sorry this wasn’t quite what you hoped it would be. :-/ To be honest when I found out it’s an epistolary novel my interest kind of dropped. I’ve been periodically trudging through the audiobook of Dracula (also told through letters/journal entries), which also has a glacial pace. (Granted, I know the writing style of Dracula is quite different from the typical book today.) Though I haven’t read or attempted to read many epistolary novels, I did like THE UNDERTAKING OF HART AND MERCY; but that only has a few letters interspersed throughout.

    • Thanks, Celeste! I generally like epistolary novels, but I can certainly understand needing to be in the mood for them! This one was harder for me than most epistolary novels since everyone’s voice was so similar :/

Geek Out:

This site uses Akismet to reduce spam. Learn how your comment data is processed.