Authority is the second book in the Southern Reach trilogy, the first being Annihilation. I would classify these both as literary science fiction, if that is a thing. Altogether very different from the first, but stylistically the same. We get to experince the story from a different character's perspective and this made the pair of books much more fulfilling. Sadly this did not make the movie any more comprehensible.
I thoroughly enjoyed this book at times, especially now that it is over. However, reading it was really a drag. It had this feeling of over writing. I don't really know where to classify this one. I am calling it okay, and I recommend it, only if you have read the first one. But I can't call it good because it was so often annoying in how it dragged on with this abstruse language. I will probably still read the last installment just to find out how everything gets tied up.