Scary books can have a wide range of genres.  Is it ghosts, vampires, werewolves that make you wake at night from the smallest sound?  How about a psychopathic serial killer on the loose?  For the horror fiction reader there are many, many books to choose from.  Some readers gravitate towards a particular genre and usually stick to reading those types of books.  Some prefer a more contemporary, modern setting and rarely ventures into gothic horror.  Some readers just love a scary story so they run the whole spectrum of genres to find the perfect book that keeps them up at night.