In his afterword the author talks about complaints he received about voices other than Jade's narrating in the first two books, so he decided to make this all Jade all the time (mostly) which I think was a mistake. Lovable though Jade is her trademark coping mechanism of turning everything into a slasher movie reference is unremitting if uninterrupted, and the habit of wandering down mental digressions of speculation and self recrimination and the nature of final girls and imagined motives and imagined acts, often while standing beside two or three people in the process of being brutally murdered, can actually get in the way and even confuse the complicated-enough actions and mysteries of the unfolding story. There's a self-indulgence to the self-flagellation and the dissociation which threatens to overwhelm the story, and they do profoundly effect the flow and the pacing. She came by them honestly, they're part of her character, but there's a tendency to wallow while the reader really wants to find out what the walking dead guy is going to do next with the golden pick-axe. This effect might have been diluted with a few other POVs, is all I'm saying. 

For all that, the book is a fine capstone to the trilogy, insane plot twists and insane amounts of bloody murder, and insane amounts of punishment inflicted on the protagonist and her friends. Will they be tempered in the fires of all this horror, or will they succumb to the curse of Prufrock? This is Indian Lake and this is Stephen Graham Jones: no-one is safe.