Originally Posted by Shopaholic
Make sure you read Legion too. I found it more frightening than the Exorcist.
Legion is one of my most favorite books of all time. There are some absolutely chilling scenes and ideas in there.
I might add that the movie version is very good as well but it cuts out the subplots which I thought were the best parts of the book. However the movie does contain a scare that scared me so badly that I had to stop it and walk away for a bit, and I've been watching horror movies since I was a kid.
My current favorite horror novel is That Which Should Not Be by Brett J. Talley. Very gothic and Lovecraftian, super atmospheric, and genuinely creepy. It's not really fast paced nor does it have a "Boo!" scare factor but the atmosphere, descriptions and sense of creeping dread are definitely chilling.