I became hooked on Harry Potter at some point between the time the 3rd and 4th books were published and have eagerly awaited each new book release since then. I like reading Harry in both the English original (my native language) and in Spanish translation (my third language).
Snape is one of my favorite characters: I wouldn't particularly care to meet him, but he is so wonderfully complicated. I also happen to be a major, MAJOR sucker for any good "redemptionist" story in which a character starts off evil and eventually redeems himself in a signficant but believable way. One reason why I like Snape so much is because I'm hoping that Rowling is going to give us something like this with Snape, even if Snape doesn't necessarily turn into a nice person full of smiles and cheer.
I tend to seek out good quality Snape-centered fan fic, though I do also read other fan fiction if they're written by good-quality authors who know their craft well.