These books expertly combine genre vibes of mystery, science fiction, eldritch horror, espionage, and more, all wrapped in beautifully written, "literary" prose. And Vandermeer's clear affection for nature buoy's all of the above, containing some of the most lovely, evocative, and creative descriptions of plants, animals, and environments/ecosystems.
Oh and Jeff just released a new Southern Reach trilogy prequel / sequel novel, Absolution. I'll be reading this after finishing a reread of the original trilogy (currently on the second book Authority). Looking forward to giving Acceptance another shot, as it was the weakest (or least accessible to me) of the three when I first read them years ago.