Evitative (Mutatum, #1)

In the summer before his fifth year at Hogwarts, Harry is drawn to a room in Grimmauld Place. Like the Gryffindor he is, he enters the room without fear. The room is a library, and Harry is surprised to find that he’s eager to learn.

Then he gets the bad news: he’s been accidentally expelled from Hogwarts, and he needs to be sorted again. Everyone is confident that he’ll go straight back to Gryffindor, but with what he's been learning, Harry’s not so sure.