More spoilers ahead if you haven't read past the 4th book....
NobelCynic wrote:
I think that Snape is atoning for his sins and the debt he owes to James Potter is now payable to Harry.
How much atoning does he have to do? Snape's already saved Harry's life at least once, certainly (when he was crossjinxingQuirrel's jinx at the Quidditch match). Plus later it's revealed that James was pretty damn nasty to Snape in a way that made Harry feel deeply ashamed about his own father. So it's not as simple as Snape just being a jerk - he has a complicated history that connects him to Harry through James. His loathing of Harry I think is quite genuine, and not just because he "owes" James - but simply because Harry IS very much like his father in Snape's eyes. And as someone who's been bullied myself I can totally relate to how it most feel to NOT be able to get away from those memories and why he'd feel the need to be defensive around Harry.
Snape's an utterly brilliant literary character. He works both as a literary character within the larger story, AND he's a revealing figure about certain nuances of human social life we too often gloss over or paint in black and white (like, "he's just a jerk," or "he's just evil"). He has substance in that he's a very grey character who's thickly in the middle of everything - he's obliged to the protagonist, Harry, and to Harry's protector, Dumbledore, while simultaneously being obliged to the villian, Voldemort, and Voldemort's "appentrice," Draco. JKR has done a fabulous job with his character arc, in making this very complex character work. He'll remain ambiguous until the end...who knows, maybe JKR will deal us a nasty blow and leave him ambiguous.
I personally am rooting for Snape to be "good" at the end. I know it's so
maudlin to hope for Snape's "redemption," and JKR has been anything but maudlin with Snape up to this point. But who knows - she's been so sharp and creative so far, she may have a few surprised left for the Snape story.