I didn't read the book, so I was confused at the end and couldn't put all the pieces together. I felt like I really needed to go watch it a second time. I love movies that mess with your mind and keep you trying to figure it out. This movie doesn't disappoint. It's not scary in a an evil way, but in a mental, creepy way. Superb acting! I can't wait to go see it again, so I can look for clues along the way.