I tried in two different occasions to read this book, and I imagine that it will absolutely dazzle the right audience. Unfortunately, it wasn't for me.

I didn’t realise that this was an epistolary novel so it took a little adjusting. Overall however, I enjoyed it once I got into it, and am looking forward to book two because I need to know what happens after that cliffhanger!

A Letter to the Luminous Deep is an emotionally impactful read told entirely through letters, which gives the story a personal and intimate feel. The two main characters connect through their siblings' correspondence as they unravel the mystery of their siblings disappearance and navigate their grief. The unique setting, much of it takes part under the sea, and world building alongside the slow-burn romance are absolute highlights.

However, the plot moves slowly, and the mystery could have been fleshed out more. The shifting timelines made it a bit hard to follow, and the ending felt rushed.

Despite these flaws, the book is still beautifully written and perfect for those who enjoy slow mysteries, emotional depth, and character-driven stories. The heartfelt connections and unique format make it worth the read.

{3.5/5]

(Thank you to Netgalley and the publisher for an eARC in exchange for an honest review)

A Letter to the Luminous Deep is an intriguing and unique read, told entirely through letters. For the most part, I really enjoyed this format — it added a charming, light academic feel to the book, especially since many of the characters are academics themselves with a clear passion for their fields. The letter format brought a personal, intimate touch to the story, but there were moments where I wished I could have experienced certain scenes firsthand rather than just hearing about them after the fact. There were discoveries and emotional moments that would have had more impact if we’d been present with the characters rather than reading their reflections on them.

The concept behind the plot is fantastic — two people connecting as they read the letters of their missing siblings, trying to understand what happened while also processing their own grief. The mystery elements tied to this were intriguing, but I do wish they had been a little more fleshed out. The story unfolds quite slowly, and it’s not until the second half that things really start to unravel, which left the ending feeling a bit rushed. The shifting timelines also got a little confusing at times, making it hard to keep track of what was happening and when.

The romance was a definite highlight. Watching the characters get to know each other through their letters felt organic and sweet, and I really appreciated the thoughtful mental health representation woven into their relationship.

My biggest issue was with the characters’ writing styles — they often felt too similar, and I sometimes had to backtrack to check who was writing to whom to fully understand what was happening.

Overall, A Letter to the Luminous Deep is a beautifully written, emotionally resonant story with a unique structure and strong character dynamics. While the pacing and narrative style had some drawbacks, it's still a thoughtful and engaging read — perfect for those who enjoy slow-burn mysteries, academic settings, and heartfelt character connections.

This is an epistolary writing style that is a tale of the deep and romance between two scholars. This romantasy is an interesting debut. The writing style was unusual and not my normal enjoyment, but I can appreciate what the author was trying to do. Would recommend if your looking for romantasy with a hint of dark academia vibes

I haven't enjoyed a fantasy read as much as I've enjoyed this one in a while. Fantastic writing; I enjoyed the whole concept of the characters exchanging correspondence and documenting their perspectives. It made the reading experience sort of real-time and very engaging, and a totally unique experience. I cannot wait for the next book! So excited!

3.5 🌟

SPOILERS

Thank you to netgalley for an arc of this (I’m very behind 😂)

I have been so excited to read this book, and the romance certainly didn’t disappoint. I adored Henerey & E’s letters and how they were able to be there for one another even only meeting twice in this book. Wher they had felt pretty alone they managed to find each other and the way they spoke of each other was just so sweet.

The writing was really interesting and I enjoyed the fact that it was all in letter form and other notes & correspondence found from others. It did keep me guessing throughout the whole book what had actually happened.

Things that I didn’t massively enjoy was that it felt very slow paced, and although I understand all the letters were building the bigger picture, I slugged through a few of them from the Ridge mission as I just didn’t find them as compelling. Sophie & Vyerin’s letters I also loved and watching their growing friendship through their siblings.

I am interested enough to read the next book, but I just have no idea what will happen and all this stuff with the Fleet and the Scholars was a bit confusing to me. My current theory is that the Fleet has most of the Challencors in on it, but we will see what happens in the sequel!

DNF'd at around the 35%. At that point I was just forcing myself to read it hoping it would get better. Such a shame because the plot itself sounds so good. I might return to this one in the future.

Thank you NetGalley & Little Brown Book for approving this ARC.

It took me a while to get into this book and even though i loved it i think it was because of the story being told by way of letters between mainly 2 characters, but once i got past the 25% mark I found it to be really magical and very calming read and I enjoyed the scientific setting that ran alongside it.

The last 30% really held my interest and i am glad I got the chance to read this book.

Thank you to Netgalley and the publishers for this advanced reader's copy and the opportunity to read this early. Review has been posted on Waterstones and Amazon.

A great light academia read that’s unique and fun! I really enjoyed the mystery aspect to the story and found it engaging!

I cannot stop thinking about this book. So far, my favourite book of the year. The mystery still haunts me and I cannot wait to read the conclusion. The world came alive under the masterfully written letters which proves the genius of the author!

Thank you for the arc. I love academia books and this light academia had me hooked too with the letter-type storytelling. I love a good slow burn and i adored the setting of this book.

This is one of those books I actually had to think long and hard about after finishing it because I was so conflicted over how to rate it, since there quite a few things I enjoyed but also at least as many I was frustrated with.

Starting with the positives, I was immediately hooked on the premise for this book: a light academia epistolary underwater fantasy mystery romance sounds like a mouthful, but also exactly like the type of book I would enjoy. Told entirely through letters, the book revolves around the disappearance of reclusive E. and scholar Henerey Clel following a mysterious discovery they made, and their siblings' attempts at making sense of this.

The relationships that develop between the different characters, which readers can witness slowly unfurling through their correspondence, were by far my favourite part of the book. Interactions between the different characters are realistic and rich, whether that's the sisterly relationship between E. and her Sophy, the budding romance between Henerey and E., or the friendship between Sophy and Henerey's brother Vyerin, bound together by grief and the need for closure. It is hard to convey such deep levels of human connections only through letters, but the author did a wonderful job of it.

The world is also intriguing and lavishly built, with many natural wonders and sea creatures being thoroughly presented throughout the book as the different characters engage in their research, and I was keen to learn as much as possible about them. What comes across as less clear in the world building is the way society is structured and functions, despite references to academia and its structure throughout. Now, it is entirely possible that this will become clearer in the next book (or books?) in the series, since this is only the first one - something which I realised very late on, as for some reason I was convinced I was reading a standalone.

What I struggled most with in reading this book were the writing style and the pacing. As the characters are all scholars or researchers, their use of language reflects this, with a prose reminiscent of Victorian English laced with academic jargon. This isn't typically an issue for me, since I'm used to reading academic papers for work, and I enjoyed other books written in a similar style: for instance, Emily Wilde's Encyclopaedia of Faeries is narrated through research journal entries and I had a great time with it. With A Letter to the Luminous Deep though, the sparks just didn't fly, and I ended up finding the style verbose and overly weighed down by unnecessary formalities, even in letters between siblings.

I was also completely unable to distinguish between the different voices, as all the characters sounded exactly the same in their writings. At one point, I had to switch to the audiobook version (which is excellent, by the way), as the production featuring multiple narrators finally allowed me to understand whose letter I was reading without constantly having to go back to check. This made me feel as though the book was just dragging along, something which wasn't helped by the extremely slow pace. Now, I generally prefer character development to plot so maybe this was a case of me reading this book at the wrong time, but I really struggled to get through it for large sections in which it felt as though nothing at all was happening. And then, everything happened all at once, ending on a pretty huge cliffhanger, which I found pretty frustrating.

I think I'll probably pick up the next book in the series since I am somewhat curious as to where the story might go next. This is also a debut and I see some great potential for the author in the next books, especially given how the relationships in this book were some of the best written I have come across recently. I also liked the queer normative society and the mental health rep (with depictions of OCD and anxiety), so there's definitely a lot to save here!

I’m officially hooked on this light academic romance set in a magical, underwater world! Told entirely through letters between two scholars, this epistolary fantasy has a unique charm that pulls you into its deep-sea mystery and growing romance. As a debut, it’s a solid start to what promises to be a series with a lot of potential.

The story begins with a reclusive scholar, E., discovering something beautiful outside her underwater home. This sparks an intriguing correspondence with the renowned Henerey Clel. At first, their letters dive into passionate discussions about their academic interests, but soon, their feelings for each other emerge. The romance develops in a way that’s both intellectually stimulating and heartwarming.

If you're an academia lover, this book will absolutely speak to you. It demands your attention with its intellectual exchanges and slow-burn romance, though I have to admit, the entire book is made up of letters—so if you’re looking for fast-paced action, you won’t find much here until the last 20-25%, which picks up just before ending on a cliffhanger.

What really drew me in was the romance and the way we get to know E. and Henry through their letters. Their love story unfolds in such a unique way, with their siblings, Sophy and Vyerin, also writing to each other, bonding over the mystery of their missing siblings. I adored their friendship and how they shared their grief through their mutual love of books and fantasy, and I especially enjoyed their discussions about their libraries.

If you're in the mood for a slow-burn, letter-driven romance with a touch of academia and an intriguing underwater setting, give this one a go. It’s a good read that leaves you wanting more.

Thank you. NetGalley and Orbit Books for the advanced copy in exchange for an honest review. All thoughts and opinions expressed are my own.

#ALettertotheLuminousDeep #NetGalley

This fantasy novel transports readers into a richly imagined world brimming with magic, mythical creatures, and epic quests. From the very first page, the author draws you into a vivid and immersive setting, complete with intricate world-building and finely detailed lore that enhances the sense of wonder and adventure.

The plot is thrilling and fast-paced, filled with twists and turns that keep you engaged. It follows the journey of a protagonist who is as relatable as they are courageous, facing daunting challenges and making tough decisions along the way. Their growth throughout the story is well-developed, balancing moments of vulnerability with displays of strength and heroism. Secondary characters are equally memorable, each with their own unique traits and motivations, contributing depth to the overall narrative.

The author's command of imagery and description brings the fantastical elements to life—whether it’s a sprawling enchanted forest, a dark and ominous castle, or a mystical artifact imbued with ancient powers. The magic system is well-conceived, with clear rules and limitations that add both intrigue and stakes to the plot. This sense of structure helps ground the story, making the fantastical elements feel both believable and integral to the characters' journey.

I started this book a while ago, but it didn't grab me. Maybe I'll finish it, but for now I'll put it in the middle of 3 stars.

DNF at 16%. The writing was so difficult for me personally I couldn't keep up.

For an epistolary novel to succeed, each letter writer should have a distinct voice. However, the four or five characters whose letters make up the first 16% (amid a rather confusing timeline, I might add) sound nearly identical. I could have overlooked this if the writing style hadn’t been completely opposite to my taste—overly dramatic, with nearly every sentence ending in an exclamation point, making every thought seem so important that, in the end, nothing felt important at all.

If you're thinking of picking this up, I highly recommend reading a sample chapter first to see if the writing style works for you. That said, I would still give this author another chance in the future, just not with this one.

The perfect mix of fantasy and romance! With light academic vibes to fill your metaphorical cup, this book was a real treat. I loved that it was told through letters; it felt like such a unique way to get to know our characters. I also really appreciated the mental health rep in this book as I feel like it's harder to come by in fantasy novels. It was handled really well by the author and definitely earned them a few brownie points from me. I look forward to continuing with this series and I think this was a great introduction to the world!

A Letter to the Luminous Deep was an enchanting and unique read. It was the first epistolary novel I have come across, and after getting the hang of it, I really enjoyed it and found the style enhanced the story. The characters were exceedingly well written, and the mental health aspect was portrayed so thoughtfully I found it helped negate the distance I was worried I would feel from the writing style. The prose was whimsical and romantic. Sylvie Cathrall succeeded in creating a vivid underwater world that I cannot wait to return to in the sequel.

“Reading your letter was an experience like no other. Have you ever considered, E., that someone ought to write a Fantasy about you?” :’)

Thank you so much to Orbit books and NetGalley for providing me an early copy to review. I had a great time, and recommend it to fans of Emily Wilde, A Feather so Black, and cozy, otherworldly fantasy.