Intensity by Dean R KoontzI notice you haven't read any Stephen King. What about The Dark Half?
I've been wanting to read a Stephen King I just don't know I good one to start with lol
I started with Firestarter. His oldest books are the best I think.
I really like the Odd Thomas books by Koontz.
Chelsea Cain's books. You already know "whodunit," but they are psychologically chilling.
Probably a bit late to the conversation but David Wellington writes horror. I can't read them at night. They are really good though. 13 Bullets and 99 Coffins are the two books I read by him.
Have you tried any of the Dresden books by Jim Butcher? They're pretty good.
the amityville horror by jay anson the exorcist by william peter blatty