Just finished Vandermeer's Absolution.
The three parts aren't even in quality -- I get what he was trying to do in the third segment, but the point of view character's internal monologue is so annoying, it's distracting -- but overall, it's very good.
The first three Southern Reach novels -- Annihilation, Authority and Acceptance -- make up, more or less, a single narrative about government agents entering into a restricted area of the Gulf Coast that is undergoing some sort of mysterious transformation. The next book then zooms back to show the government agency behind the expeditions. And then third shows the consequences of the past two novels as the area begins to spread. The third novel ends with the threat of Area X potentially consuming the world, although that doesn't seem to have happened yet in the fourth book.
The fourth book jumps back in time before the first novel and then after the third, but mostly serves to examine a single mysterious figure in and around Area X, although it took a little while for me to realize that was what the book was largely about. And the book ends a little ambiguously, with me thinking we're going to see the origin of the figure but stopping just short of that.
It's impressive that after years away, Vandermeer doesn't make the mistake the back half of Lost did, IMO, with explaining too much of the mysteries. Yes, readers now have a better idea of what's happening in Area X -- maybe -- but even then, the details and the why are, at best, conjecture. And the figure featured throughout Absolution is basically yet another character caught up in all of this, rather than a man behind the curtain capable of explaining everything, even if he wanted to.
Even more than the earlier books and the movie, this very much feels like climate change as a horror story, although "horror" is probably a bit too strong a word here. There's a seemingly inevitable doom, an idea that the modern human world will eventually be overwritten and -- especially in the second and fourth books -- human arrogance that they can somehow fix all of it, even as the reader knows that simply will not happen.
This isn't an essential book for anyone who liked the previous novels, but is more like a small dessert after the first three books.