The Descent by Jeff Long
My rating: 5 of 5 stars
I gave this 5 stars not because it was perfect, but because it did what any good book should do - it made me want to keep reading. One night I read it until 3.30am, I just couldn't stop. Other times I would find time to read a chapter rather than do something else. Only a minority of books have this effect on me, so it deserves the highest praise.
The opening chapter is the best one in the book. Mystery, twists, economical writing, and a descent into tension and then really convincing horror. This is a high mark - it obviously can't be this good for the whole book, but the novel goes on to take you in directions you didn't expect, and you still want to read on. If anything, the horror element fades out slightly: the more we learn about the Hadals, the less scary they become, and in comparison the humans seem more and more to be the monsters. It's a nice twist, but switches the novel from horror to thriller. Still compelling, but less likely to give you nightmares.
As other reviewers have noted, the novel is full of themes and subjects, an ambitious amount that few authors would try to incorporate into a single work. And, generally, it works well. It is part of the unexpected nature of the novel, with the twists and abrupt changes almost representing the twisting and broken tunnels beneath the earth.