It by Stephen King. Don't get me wrong, I loved the movie, but because it was a series for tv, it was toned down a lot, and the "special effects" for the monsters were way too cheesy. I LOVE the book, I've read it about 20 times or more over the years, so I was very picky about the movie.
Oh, and looking at something in reverse, there was once (just once) a movie that I liked better than the book. That never happens! I loved The Color Purple, but I can't stand the book for some reason. I don't like the style, and there's not much to it.