I mentioned this book in the comments a bit back. The rules don't seem to forbid this kind of post.
The book is Peter Watts'
Starfish, book one of four in the
Rifters "trilogy" (the US publishing cartel thought the last book was too long and made Watts split it up into two volumes, about which fact Watts bitches mightily in a foreword to the third book). Imagine the wacky, huge-toothed deep sea creatures we've seen posted here. Now imagine them ten or twenty times bigger, and you're working on a geothermal vent power station surrounded by them. And the reason they're so big? I won't tell you what it is, but it could end humanity.
Watts isn't so good at writing action. I'll put that out there right now. But tension, that he does well. Scientific believability in his fiction is something else he does well. Biogeeks in the house should love this book.
For a taste of his skills, go look at
this amazing presentation that he gave at a Toronto science fiction convention in 2005.
To close, if you liked the presentation, you might also like Scott Westerfeld's
Peeps, a book that manages to present vampirism as an evolved relationship between a microscopic parasite and normal humans. The book alternates chapters between the actual story and lovely information on parasite life cycles and parasite-host relationships. I think that mentioning two books breaks the one-creature-per-post rule; sorry about that.
Edit: Mod and member comments welcome regarding whether or not this kind of post is okay in the future.
Edit: Peeps link is fixed.
Edit: General concensus is that fiction posts fail here.