I usually find it pretty tough to do justice to a GOOD book in a movie, at least when it comes to horror. It's easier to make an action book into a movie.
Steven King's "Christine" is probably one of my favorites. "Bram Stoker's Dracula" is up there too, with the exception of wanting to strangle Keanu Reeves for his phony Brit accent. And my personal favorite "Queen of Damned" though most of that for me personally is the soundtrack.
Any candidates out there?