Yeah he has a bunch of novella's like this that are marketed for young adults (teens). Most are labelled as Fear Street - a series marketed for teens. But there are a few like this one that aren't labeled as anything and are just stand alone novels. I think he wrote the first ones thinking that he would stop there but then realized the new market of older readers and created "fear street" for them - probably using ghost writers, I'd imagine.
RE: The Boyfriend by R.L. Stine