Dan Simmons has written in so many genres, it's hard to imagine that all of them could be good, but they really are. I've already read The Terror, a supernatural thriller, Drood, a mystery involving literary legends Charles Dickens and Wilkie Collins and Hyperion, a Sci-Fi thriller. 
 I would place Summer of Night in the horror genre. It isn't a genre that I read often, but Simmons has a way of developing charaters that you really care about and suspenseful enough that it's hard to put the book down. 
 This story is about a group of friends, a creepy school marked for demolition and what happens inside the school that summer. When the strange happenings start spilling out into the town and affecting the friends, they have no choice but to investigate and get involved in solving the mystery. 
 Another good read!