This book was praised by more than one of my acquaintances who are not writers. It is an important distinction. I have been increasingly disappointed by new books recommended by science fiction or fantasy writers, and have come to suspect that those books are hyped because of something other than good storytelling. But I know that if my nonwriter friends enjoy a book, it must have an engaging plot and characters; and if they are techies, it probably has well thought-out, science-based (or at least systematic, even if magic-based) worldbuilding.
"A Darkling Sea" has a lot of that. The worldbuilding is superb, and it has plenty of intrigue, as its human protagonists deal with not just one, but two very different alien races. Yet I was ambivalent about this book. It left me with a strange feeling that the majority of the plot was just the setup for something that didn't quite happen. But it is not true, of course: the plot arch arched satisfactorily, and was properly resolved in the last couple of chapters. So it must be that my expectations were different.
While this book shows a clash between two technologically advanced races, it is positively NOT a space opera. The action is carried out guerilla-style at the bottom of the sea on a distant planet. There, a group of human researchers observe Ilmatarans -- underwater, bottom-dwelling intelligent beings -- until another alien race, Sholen, tells them to quit or else. It is really about a conflict between human and alien psychology. But it rather lacks intensity and sharpness of psychological conflicts that such a claustrophobic setting could -- or should -- provide. Then again, my measuring stick for similar themes -- humans living in close quarters, isolated from civilization, facing the unknown -- is Peter Watts' "Blindsight". Few novels live up to the intensity of "Blindsight", so perhaps it's not fair to measure "A Darkling Sea" against it.
Still, when the driving force of the plot is a conflict between human and alien mentality, the book needs better characterization. As it is, the characters in it (the humans at least) are likeable, but bland. There aren't any strong, quirky characters through which such a conflict could manifest.
The worldbuilding in this novel, however, is excellent. It's not an easy feat to create two credible, different, nonhumanoid races, but this novel did just that. Between the Ilmatarans and the Sholen, Ilmatarans are definitely a more completely fleshed-out civilization. The name Ilmatarans is the only thing incongruous about it, because this name brings to mind J. R. R. Tolkien's Middle Earth. That's unfortunate, because the lobster-like, underwater-dwelling Ilmatarans couldn't be more unlike Tolkien's elves. Other than that, their culture, mentality, customs, even speech idioms follow from the physical conditions of their world. Living at the bottom of the ocean, they don't have eyes (which would be of no use in the perpetual darkness), and instead perceive the world and communicate via echolocation and taste. As with every alien species, a writer has to straddle a careful line between making them boringly human-like, and making them too alien for us to understand. With Ilmatarans, the author fell back on a tried-and-true method of making them a pre-industrial race, akin to a medieval, feudal society on Earth; they were starting to engage with the world scientifically, but their societal structures were quite primitive. That way, as alien as they are, they are still simple enough for us to understand.
What especially intrigued me about Ilmatarans was their number-speech. They assigned non-obvious semantics to numbers, and considered not just factorization of a number, but also its decomposition into a sum of integers; from that they inferred something about a person's character. Too bad it didn't play a big part in the book; I would have liked to know more about that. Even though there is no scientific basis for such a cabbalistic approach, it could tell us a lot about a culture.
But an even more interesting race was Sholen, the spacefaring civilization that clashed with humans over the sphere of influence. They were a spaghetti ball of intriguing contradictions. They had a self-proclaimed "hands-off-the-universe" attitude, which meant they wanted uncontacted alien races to remain so, and especially to stay free of influence of humans -- yet they enforced their peace philosophy rather aggressively. Their social structures and modes of interaction were a bit like bonobos', but they were nothing like the friendly, frolicky apes. My impression of them was more like hulking, menacing, six-limbed monsters. Despite all that, Sholen did not seem to be a poorly thought-out heap of inconsistencies, but a complex race with its own internal logic.
While the novel was enjoyable, it wasn't exactly groundbreaking, and that's why I will only give it 4 stars. I like to reserve 5 stars for books that do something innovative, such as develop an original scientific or philosophical idea. (Yes, like Peter Watts "Blindsight"). The setup, storytelling, mood, and characters of "A Darkling Sea" strongly resemble classical science fiction. An comparison that comes to mind is "Dragon's Egg", which also has primitive but smart creatures living in an extreme environment (super-high gravity of a neutron star). It is classical in the sense that science and technological resourcefulness takes precedence over character depth; the human characters in the book are not especially interesting. But the book is at least modern in the sense that female and male characters are equal in skill and courage.
I also have one minor beef with this book. The ending reveals a surprise whose impact can only be fully understood if you kept track of tiny, insignificant pieces of information scattered throughout the book. At least that's my guess. When I read the last sentence, I thought "huh"? What's that have to do with anything? Is the object mentioned in there referenced anywhere earlier in the book? If it was, I quickly forgot it (it was no more than a minor detail), and I don't even know how far back I would have to go in the book to find earlier references. Or is there an implication that this object could only have been left behind by yet another, ancient, long-lost civilization? If so, it must be a setup for a sequel, because this object played no role in the book that I could tell. Luckily, the plot had already been wrapped up at that point, so the ending was just a bonus "huh".