Harry Potter and the Half-Blood Prince
Harry Potter and the Half-Blood Prince (released July 2005) is the sixth novel in the Harry Potter series by J.K. Rowling. The book explores Lord Voldemort's past and the suspense of Harry's many ongoing conflicts.
A new character is introduced, Horace Slughorn, formerly head of Slytherin House and Potions teacher at Hogwarts, he replaces the sinister Severus Snape as Potions Teacher, although Snape remains head of Slytherin and becomes Professor of Defense Against the Dark Arts. Harry ends up doing very well in potions, with the help of a book by a former Hogwarts student before Harry's time named the "Half Blood Prince". In the end it turns out that is a schoolboy nickname for Snape, Harry's nemesis, and Snape murders Dumbledore and flees with Voldemort's supporters. Snape is replaced as head of Slytherin house by Slughorn.