Could anyone tell me the name of the book in which Dumbledore makes Harry stay with Snape when he finds out about the Dursley's abuse or something, and while staying with Snape, he finds Lily's journal where he finds that he is actually the son of Lily and Snape. He goes to Hogwarts as Snape's son and other things. He also becomes very powerful practising things with Snape over the holidays.