A final rush, and a leap of faith
Ties together loose threads from "Annihilation" while opening up several possibilities for the next novel in the Southern Reach trilogy.  The first novel was pretty trippy and paranoid; "Authority" is more of a character study of the Southern Reach's new director; the tale is told from his perspective.  And Area X  gets a whole lot stranger!  Methodical, with many non-sequential jumps in the story, ultimately leading to a final rush over the last few chapters where I couldn't put the book down.
I was on the edge of my seat the entire time. Which path would Mary choose? It gives great perspective on the school-shooter phenomenon. I did not expect the ending.