I'm looking for this book (I think it was a Goosebumps book) with a boy who leaves his body and does all sorts of things like float around school. I think he leaves his body in a closet or something... Anyway, someone else does the same thing, and there is some sort of conflict between them. I forgot the title, but would very much like to read it again. I think the end involved his dog too... but I'm not sure.

I remember a goosebumps book about a boy who becomes invisible with the aid of a mirror, and I believe he had a dog too. Could this be it?

If not, you could try finding a list of all the goosebumps books (amazon would do) and check them one by one to see if you can find it. Good luck!