The fact that he put all of his books together from the start of his career makes it all fit together well, as opposed to if he claimed they were all a connected world later on. That explains the common figure of Randall Flagg. He is just behind Pennywise when it comes to creepy villains from Stephen King.
Yeah, Tim Curry was the perfect Pennywise.
The movie was pretty true to the book. You don't see that a lot.