Harry Potter and the Half-Blood Prince is a fantasy novel written by J.K. Rowling, which is the sixth book in the Harry Potter series. In this installment, Harry Potter and his friends, Hermione and Ron, return to Hogwarts School, where Harry discovers a secret book that belonged to the "Half-Blood Prince." Through this book, Harry learns new magical techniques and fights against the dark forces that threaten the magical world in the form of Voldemort.