Wow! Intense! Obsession is the right word in here, it shows on both their face; though on Harry's a bit of surprise is mixed, like his asking himself if he is really seeing Snape's ghost or an hallucination, something that he wasn't expecting to see but wanted to anyway. And Snape... well, it's Snape, only obsessed with his work (all those sheets on the wall) and books, but that's not where his looking at. The red is a nice touch, we can hardly guess if that's blood or Snape's red ink (the one he loved to grade essays with) on those hand prints and writings.