... has been described as an eco-dystopian thriller, but it’s something slower and more meditative ... Nayler’s poignant, mind-expanding debut is full of artificial intelligences, with various levels of mindfulness, alongside the mysterious octopus community. The juxtaposition of these nonhuman minds raises big questions about the nature of consciousness.

Orbiting [the] central story are two suspenseful subplots whose connection to Ha’s storyline are only slowly revealed ... A novel that wears its themes on its sleeve, but the ideas it tangles with...are so intriguing that this hardly matters ... Has some talky patches, especially the parts where Ha and Evrim hash out the meaning of the team’s work. But Rustem’s and Eiko’s parallel storylines inject action into the novel while sustaining Nayler’s point that humanity needs to get its own house in order before it starts looking for company in the universe ... It’s unsurprising that the novel does briefly tip into didacticism about how people ought to care more about one another and the environment. Still, the imaginative stretches the novel calls for—the consideration of what shapes minds might take in bodies radically different from ours—make up for the occasional finger wagging. His octopuses are so much more than teacherly dispensers of life lessons, and fortunately, this wondrous novel is, too.

Exceedingly ambitious ... The dystopia Nayler captures is resolutely believable ... The problems that afflict The Mountain in the Sea are a consequence not of its premise, but of its scope and magnitude: information dumping, the occasional explanatory monologue, story lines that are only tangentially connected to the main arc, and lack the same level of interest ... Regardless, Nayler’s charm lies in his belief in the very human qualities of attentiveness and self-doubt. The result is a novel that is alert, intelligent, open. At a time when we are oversaturated with dystopian narratives, Nayler’s distinguishes itself by being almost devoid of cynicism.

As the Nagel citation would suggest, one of Nayler’s master themes in this convoluted adventure is the enigmatic nature of consciousness, so it makes perfect sense to use the octopus as foil for and analog of the human mind ... It is a difficult thing, though, to take the filmy, incidental feeling of faddy interest and make of it something rich and colored-in, deep and dimensional, more lasting and compelling than a viral video. I’m not convinced that Nayler’s attempt fully achieves that ... the hologram of his writing starts to glitch if you read too closely. The same figures of speech are repeated ad nauseam ... Violent imagery (of which there is no short supply) is expressed in terms so curious as to become funny ... It’s not that Nayler can’t write. The short paragraphs from the invented nonfiction books by Ha and Mínervudóttir-Chan are, by contrast, lucid and lovely—I’d eagerly read them in full, if they existed. And his many interests here are fascinating, especially in the way he’s tangled them up together ... It did not bother me so much that these topics are as algorithmically tuned toward a reader like me as the very idea of an octopus novel is; this is a case where the algorithm has won, all these things tingle every pleasure center in my brain. Nor that, ideas-wise, Nayler has basically just remixed some of recent trade nonfiction’s greatest hits. What bothered me was the cool glassy thinness of it all ... It’s the intricate lacework of feeling Miéville manages to elaborate that I was missing from Nayler’s book, which ends with a tidy moral lesson...Doesn’t such a moral require a profundity of feeling? ... There’s much good argument against reducing all the possibilities of literature to the trite humanistic application of empathy-building. But at the same time, how exquisite it would be, to feel an octopal overwhelm at the yawing of meaning—and what besides the world-splicing of writing could let us surmise that?

Advertised as a thriller, but readers expecting high suspense and a predictable storyline will be disappointed. The novel is slow, thoughtful, and does not tie its loose ends into neat bows. The various storylines come together only thematically, and some of the point of view characters never meet. However, as a literary exploration of consciousness and the peculiar traits of humanity as a species, it succeeds wonderfully ... Nayler wisely reaches no neat conclusions at the end of his tale; instead, the reader is given multiple avenues to contemplate how invention inevitably serves both creation and destruction, how the values of a civilization do not necessarily reflect the values of its individuals, and how vast the communication gulf can be between thinking, conscious minds.

This compelling sf debut is impossible to put down, a delightful embroidery of the rush of scientific discovery and the pain of isolation, asking hard questions about what society is and what it means to truly understand another creature.

Nayler’s masterful debut combines fascinating science and well-wrought characters to deliver a deep dive into the nature of intelligent life ... Nayler provides a tightly focused framework for the challenges Nguyen faces as she attempts to decipher octopus language and culture, which will especially please science-minded readers. Subplots featuring genius hacker Rustem and Eiko, a man trafficked into slavery aboard a fishing vessel, expertly weave into the narrative while also offering readers a broader understanding of the political and technological state of this near-future world. As entertaining as it is intellectually rigorous, this taut exploration of human—and inhuman—consciousness is a knockout.

Nayler maintains a cool, cerebral tone that matches up with the story's eerie underpinnings. Less an SF adventure than a meditation on consciousness and self-awareness, the limitations of human language, and the reasons for those limitations, the novel teaches as it engages. An intriguing unlocking of underwater secrets, with the occasional thrill.