It hooked me right from the beginning but the resolution wasn't really shocking (although I did like how even the tiniest things were connected/added up to the big thing). 
 Spoilers for Gone Girl and Dark Places: (view spoiler)[Am I the only one tired of the man not telling on his girlfriend's psycho behavior because she's pregnant with his child trope?? The autor did that both in Gone girl (Nick and Amy) and in Dark Places (Ben and Diondra) (hide spoiler)]