Fahrrenheit 451...good book. Read it twice. (also enjoyed 1984, but never got to anthem).
As for Snape, I'm happy someone else thinks he's not a death-eater. He had to kill Dumbledore due to the unbreakable vow (and the fact that Malfoy couldn't have done it himself), and if he didn't make that vow, the death eaters (who already didn't trust Snape) would have gotten rid of him right then. Snape, being as he is, was in a tight spot the whole time. Also, he would have to run at the end (note how he never hurt Harry, but actually protected him during his escape) because he killed Dumbledore, and everyone was after him and Malfoy.
This is what I think, I may be wrong, but we'll just have to wait and see...