The Half-Blood Prince's Book

In their first Potions lesson with Slughorn, Harry and Ron, who did not buy new textbooks, are given old copies from the cupboard. Harry's copy is filled with handwritten notes and corrections by a previous owner, the 'Half-Blood Prince'. Following the Prince's instructions, Harry successfully brews a Draught of Living Death, winning a bottle of Felix Felicis as a prize. Hermione is suspicious of the book, but Harry defends it. Later, Harry discovers the book is inscribed 'This book is the property of the Half-Blood Prince'. He becomes intrigued by the Prince's identity and the many spells and potion tips written in the margins.