I only ever read two books from the Goosebumps series, but one of them left a huge impression on me, and I cannot recall the name. Googling the plot did nothing to help, either.

The story was a boy stays with relatives, I think, and there's a werewolf in the woods nearby. It turned out to be some kind of werewolf skin that the relatives put on...? It was kept in a box, and the boy finds it... Agh, that's all I can remember clearly. That was the very, very first (and one of the only) things I wrote a fanfiction for, because I wanted to know more about cool werewolf skin powers that change you into a beast.

Does anyone *cough*Gen*cough* know what volume this was? Am I crazy, and making it up entirely?