I was totally into R.L. Stine when I was younger, but I read the Fear Street books....by the time Goosebumps came out, I was already about 13 or 14 at least, and they were a little too pre-teen for me. If you can find it, I'd recommend reading a book he did called Fear Hall: The Beginning. It's got a great twist at the end.
I've heard about The Sitter. I've been searching for it for a few months, but haven't had any luck. I read Superstitious, the first adult novel he did, and it was an entertaining read, if dumb. Now that he's not pumping out two books a month, he can probably spend longer on developing stronger work. Perhaps he could fill the void left by Richard Laymon (Superstitious reminded me in places of Laymon's work).