This is SO beautifully written; I love the way the entire piece flows. The first person POV is incredibly effective here; it really feels like the flow of Harry's thoughts as he remembers the events at some later point in time. The opening lines perfectly describe the way half of fandom feels about Snape and his "death", I think. Harry's obsession is fantastic, and Snape, still snarky and cold and (outwardly) unchanged by the events of HBP/DH is perfect. Guh, the sex at the end. Harry utterly demands it, knowing full well that Snape won't be gentle, and Snape gives him precisely what he wants. This sort of unspoken understanding is what makes this pairing so amazing.