A letter to the luminous deep

A Letter to the Luminous Deep by Sylvie Cathrall 

Orbit Books, pb, £14.95

Reviewed by Catherine Berridge

This epistolary novel is both a love story and a mystery. It is set in an underwater kingdom. It seems that human civilisation once lived as we do on the surface of Earth and also in the clouds, but that at some point, there was a terrible catastrophe, and now all human civilisation is based beneath the waves.   The focus is on universities. One university is referred to as The Boundless, and its inhabitants are referred to as scholars. The romance of this novel, between E. Cidnosin and Henerey Clel,  is set against the backdrop of a scholars’ expedition to an underwater ridge. At some point, there is a terrible happening, and our two romantic heroes die. Their story is then told in the form of letters they leave behind. 

I found this novel to be an enchanting read, with good characterisation and a gentle pace. The mystery at the heart of the novel unfolds slowly. The worldbuilding, in constructing an entire civilisation whose focus is beneath the waves, is highly imaginative and complete. I can honestly say that I have never read anything quite like this book before, and I mean that in a positive way. It is a highly original work of art. 

One of the main characters, E. Cidnosin, is also suffering from what must be an anxiety disorder, and the book, therefore, contains a very sensitive description of mental illness. Both what it must be like to suffer from this disorder and the impact it must have on a life, therefore taking the disorder seriously, but also letting this not be the defining feature of E. Cidnosin.

I was also very impressed by the poetic quality of the language. Aquatic metaphors were often used, and this helped with worldbuilding. For example, when wanting to write about a topic at length in a letter, Henerey Clel says

“…I found myself tempted to spill a full squid’s worth of ink…”

We often refer to outer space as the final frontier, but it is also often forgotten that there is another frontier on Earth, the deep ocean, and the almost alien life that lives there. This novel does justice to that second frontier and is also a very enjoyable read. I am also happy to note that there will be a sequel to this book, called Book Two of The Sunken Archive, due out in 2025. “A Letter to the Luminous Deep” is a novel I would definitely recommend.