I'm not entirely sure that this book should be classified as science fiction. In the strictest of senses, yes, this is science fiction in that our protagonist is navigating an entirely nonhuman landscape that, although I'm assuming to be part of Earth, could definitely be classified as 'alien.' 
 Reviewing this book is proving difficult. Let's start with the basics. 
 For a good number of years now, mankind has been sending expedition teams of specialists into Area X for research and reconnaissance purposes. However, something seems to go drastically wrong with every team. They all are killed by something inside Area X, they all go insane and have a shootout killing each other, they all return hollow shells of their former selves before dying of cancer some months later. We are now on the 12th expedition. You might ask yourself, "why do we keep going back into Area X?" Great question! You're not going to figure that out for a while. Just roll with it for now. Annihilation follows the 12th expedition which, unlike the other expeditions, is comprised wholly of women: a psychiatrist, a surveyor, an anthropologist and our narrator, a biologist. One of the things I found very interesting about this book was the fact that none of the characters had names. Names in general seem rather pointless and given the context of the dangers and mystery surrounding the expedition, it is more informative to refer to the four women by their profession rather than their given name. 
 And that's about all plot wise I can put into summary. It's not for fear of spoilers, although there are definitely things you learn as you progress in the book, but it's more that the book in and of itself is rather hazy and difficult for me to figure out. It's like the book is a metaphor for the strangeness of Area X; I have problems pinning down exactly what I was supposed to be feeling throughout the book or what its purpose was. This normally would be a massive detriment to the book but there was one major thing that was a shining bioluminescent beacon amidst all of my confusion: Area X itself. 
 We as the audience go into Area X knowing about as little as the biologist knows, which is to say, we know vague generalities that the expedition control center told her. But as they explore more and more of Area X and see it take on a completely unearthly life of its own, I was enraptured by how..... strange it all was. The first thing we as the biologist come across is a strange tower/tunnel that has plantlife growing on the walls that is forming a script writing out sentences in english. In a place that hasn't been mapped out by previous expeditions, implying no human contact, we have plantlike tendrils like moss or vines growing on stone walls to form human sentences. THAT'S FASCINATING. I WANT to know more about what is happening in Area X. What events lead up to its existence? Are we actually on Earth like I assumed or is this some other planet entirely? How is Area X doing all of the fantastical things it's doing? What does its existence mean for the rest of humanity? WHAT IS ALL OF THIS? Unfortunately the book doesn't have many answers for us. 
 I feel like the book would have benefitted from being all three volumes in this trilogy compiled into one anthology. Obviously I could change my mind on this after I read the next two books but as of now I think one big book with 3 parts would have been more cohesive than 3 separate books. Both a positive and negative about Annihilation was the limited perspective. On the one hand, I loved the unreliable narrator aspect of what the biologist was telling us. We KNOW that Area X has contaminated and controlled the actions/observations of previous expeditions so you never really can be 100% sure that what the biologist is feeling and observing meshes up with what everyone else is observing. This insular viewpoint also gives us a firsthand look at what Area X does to people for their perspective. It wouldn't have been the same to be an outside observer, just watching these people interact and react to Area X. But conversely, this insular viewpoint limits what we can learn about Area X as we're stuck with whatever the biologist finds interesting at the moment. There were a lot of times that I was frustrated because I so desperately wanted to know more about something and the biologist just... wasn't that interested in the same thing I was and didn't continue exploring that. This brings me back to the anthology idea. If this was one book made up of separate parts, the picture we'd get of Area X would be much clearer as it looks like each part will be narrated by different people inside of Area X (unless of course I'm completely wrong and book two somehow still follows the biologist. Not exactly certain how that would work out but it's not by story). But imagine: one book giving three different perspectives of Area X. As a whole, the reader would learn a lot more and yet would still be able to have the intimate gaze from inside each person's head as the explore and react to Area X. It'd let the setting and landscape do all of the talking and I'd be able to rate this book a lot simpler. As it stands, I have no idea what to make of this book because it feels unfinished. It feels like these three books should be judged as a whole and since I haven't read the other two, I can't say for certain how this one is. However, the wonderful setting and creepy dynamics between the characters and themselves as the environment looms every present over them makes me rate this highly. For now at least. I still have a TON of questions that I hope will be answered. 
 Also, quick aside as I didn't know where to fit this criticism in, but I never could understand the imagery of the tower/tunnel. I don't know why we even had the two different classifications for it. I kept waiting for it to mean something but.... it never did. And just as the biologist could never think of the structure as anything but a "tower" I couldn't wrap my head around the concept of something simultaneously looking like a tunnel AND a tower. I really don't think this was an instance where one person was seeing something different than the others. I have no proof of that, it's just my gut feeling. I think that they all were seeing the same thing but the biologist only could think of it as a tower for unknown reasons. I suppose there's something to be said about the symbolic meaning behind a tower vs. a tunnel (one leads you down into ignorance and darkness while the other is generally seen as moving upwards towards the heavens and enlightenment) but I didn't get a heavy symbolism vibe from the rest of the book's imagery.