Those who know Garland's name might remember his tightly crafted Ex Machina which was a chamber piece that focused keenly on questions of A.I., what makes us human, and female objectification. Annihilation is far more expansive in every way - a larger setpiece, a larger cast, and for better or worse, a broader thematic structure as well.
As Lena's group starts to encounter anomalies, the effects of being inside the Shimmer fragment their selves, interrupting the flow of reality in the movie. Like its characters, Annihilation self-refracts, although it's a gentle mutation. More than anything else, Annihilation feels like a fever dream and a sort of descent into madness. At times, it can be seen as a metaphor for addiction or any of the other impulses that destroy humans.
Annihilation lacks the razor-sharp sense of purpose that Ex Machina had. Garland's first movie was more self-contained. However, that doesn't mean that Annihilation lacks purpose. It touches on human impulses just as much as Machina, and how creation, survival, and growing or evolving as a being often requires that sort of destruction. I doubt Garland wants to hint at a maxim or leave us with a thematic statement. Like so many of his characters, his answers to these questions might be "I don't know, I don't know, I don't know." And still, he makes his self-destructive motif clear in every facet of the film, whether it's in the set or the characters or the biologic implications that are repeatedly alluded to.
Natalie Portman is the perfect actress for the role -- able to evince a character that is used to being in control of herself, whether it's her facade or her steely unblinking stare as she guns down a monster. She's done this in Black Swan and even as Jackie Kennedy in last year's film. And it's because of this, we see more easily what an erosion of that self is. Similarly, we see how even physically, the posture of brash Anya (Gina Rodriguez) deteriorates, as she consistently seeks a seat more and more as the movie goes on. We see that destruction in different ways, and especially in Tessa Thompson's laudable performance as one of the other team members.
Annihilation is the weakest when its framing structure comes into play -- an ongoing interview that is supposed to give structure to the film, but unfortunately comes off as mostly trite. It also goes against the grain of the story, which is a slow dreamy exploration of madness. Throughout the movie, you're often caught off-guard with how weird it is and yet how well it flows. Garland has somehow allowed us to take a journey into the bizarre without being turned off. And then an interview scene comes back in and disturbs us from that reverie. It's as if someone had decided to regularly interrupt portions of Apocalypse Now with a banal interview.
Similarly, Annihilation's attempts to root the movie in reality make us beg more pertinently some plot points that don't make sense -- tactical errors that shouldn't be made by someone who served time in the army and failures of common sense. However, if at all possible, Annihilation might be a movie that's better because it's vague -- there's little sense trying to make dream logic. Unlike Cloverfield Paradox, which also came out this year, there's not a throwaway "this is another dimension so anything can happen", but it's more plausible that the characters here aren't able to understand fully what is happening because they're becoming more vague themselves.
Immense kudos to Garland for allowing himself to get truly strange. There's beauty and cerebral wrestlings, but more than that, this is an illusive film that dares to ask more questions than it provides answers.