I enjoyed this one, if one can really say they enjoy a book of the sort that Gillian Flynn writes. I thought it was much better than Gone Girl, although I still liked Sharp Objects better.
Dark Places deals a lot with the Satanic Panic. The main character is not a terribly nice person, but not a terrible person, and despite her admitted meanness, I found myself liking her and wanting her to find some sort of closure if not happiness. I don't really expect happiness for characters in Gillian Flynn's books.
Much like in Gone Girl, most if not all of the characters just were not very likable. Sharp Objects had one or two that I managed to like, but that was clearly the exception. It may also be the reason that one is the one I liked best. So, expect to read about a lot of interesting characters who range from unpleasant to just abhorrent.
The mystery in this one was good. I was really drawn in to see how it would unfold. I don't think it's possible to guess at how things went until one has read a good portion of the book, at least.
I definitely would recommend this book to fans of Gillian Flynn. As for those who have not read her, if you like psychological mystery thrillers, give it a try. It's very dark, but very well-done.