This gets rated on a different scale as it's Stephen King, and he's written some of my very favourite books. The story, characters and writing are wonderful. This is about as three-dimensional a story as it gets. I wished I'd read this before I'd seen the TV adaptation (which I've seen a bunch of times - it's a fair representation of the book), as there were no real shocks here for me. 
 PS. Pennywise will always be scary.