(BIG Spoilers for the movie obviously.)
Annihilation is a SciFi film that is as terrifying as it is beautiful. The film is something along the lines of Andrei Tarkovsky meets John Carpenter - The Thing meets Solaris*. It has all the trappings of a B-horror movie complete with expendable cast members and freaky monsters. But then it evolves into this surreal avant-garde showstopper of a finale. The movie has a folksy acoustic guitar soundtrack that slowly mutates into a bellowing synth nightmare. What you're left with is not the movie you started with. Annihilation is the kind of experience that shoves your brain into a blender and asks you to pull your mind back together again. It's weird on an awesome scale.
But what is Annihilation? That's... gonna take some writing. I can tell you up front that I love this movie. 2018 is still fairly young, but this is probably Movie of the Year already. However, I would not fault you for missing the message or maybe concluding that there isn't one at all. Annihilation doesn't have a villain with a goal or much of a shape. And unlike most SciFi films it doesn't have an easy morale like "robot slavery is bad" or "global warming will kill your children". Even a few critics like Inkoo Kang of Slate seemed totally lost at the end of Annihilation. She dismissed it as "just a mindscrew". Well, I think it's quite a bit more than mindscrew for mindscrew's own sake.
I imagine in a few decades, Annihilation is going to be one of those "pet theory" movies. The Shining is probably the best example of that kind of thing, as seen in the bizarre documentary, Room 234. The Shining is basically just a haunted hotel movie set around a badly dysfunctional family. But throw in some Stanley Kubrick touches and some details that don't add up and then you have legions of fans obsessing over it, seeing everything and anything. The Shining could be about Indian genocide or faking the Moon Landing or a really great flapjack recipe. Annihilation once its been dissected can also be about anything you want. The question is, what do I see in it?