The narrator of this opening volume of VanderMeer's Southern Reach trilogy is nameless. We only know her as the biologist. In fact, there is a curious lack of proper names in Annihilation, a hint that something strange is going on. The narrator is part of a small expedition into Area X organized by an equally mysterious organization known as the Southern Reach. We're told that something happened in Area X about 30 years ago. Southern Reach has started sending in expeditions to learn more about the area, but none of them has been successful.
The biologist, a singularly unsuccessful specimen of her type, is one of four on this trip along with a psychologist, an anthropologist, and a surveyor. Their journey begins by crossing the border, an experience that requires hypnosis for them to "remain calm." After setting up at base camp, the four find a tunnel that contains only an unknown life form that lives on words scrawled in an unknown substance by an unknown entity. The anthropologist disappears that night. The psychologist appears inexplicably tense. And the biologist learns that the psychologist has been controlling the rest of the party through post-hypnotic suggestion. She is immune because of a spore she accidentally inhaled back in the tunnel, which she insists on thinking of as a tower for some reason.
With the revelation about the hypnosis, the biologist realizes just how much she's been lied to. And I started to realize how powerful words and names could be. There was supposed to be a fifth member of the party, an linguist, but the psychologist tells the group that she didn't survive the border crossing. The words in the tunnel are a bizarre ramble of pseudo-religious verbiage. The only proper names in the book are for Area X and Southern Reach. Without a linguist and without proper names, it's very hard to pin down just what things are. That's what a name does; it distinguishes this from that. Without those names, the entire novel has a strangely hypnotic tone.
The expedition falls apart, just like all the others that came before. The biologist abandons her task of categorizing the flora and fauna of Area X to investigate why the psychologist and Southern Reach are lying, and what happened to the previous expeditions. There is a conclusion to this book, but we don't learn many concrete facts in Annihilation. The rest of the mystery is left to the other two books to unravel. All we can say at the end is that something is deeply wrong.