- Chapter 1: The Other Minister
- Chapter 2: Spinner's End
- Chapter 3: Will and Won't
- Chapter 4: Horace Slughorn
- Chapter 5: An Excess of Phlegm
- Chapter 6: Draco's Detour
- Chapter 7: The Slug Club
- Chapter 8: Snape Victorious
- Chapter 9: The Half-Blood Prince
- Chapter 10: The House of Gaunt
- Chapter 11: Hermione's Helping Hand
- Chapter 12: Silver and Opals
- Chapter 13: The Secret Riddle
- Chapter 14: Felix Felicis
- Chapter 15: The Unbreakable Vow
- Chapter 16: A Very Frosty Christmas
- Chapter 17: A Sluggish Memory
- Chapter 18: Birthday Surprises
- Chapter 19: Elf Tails
- Chapter 20: Lord Voldemort's Request
- Chapter 21: The Unknowable Room
- Chapter 22: After the Burial
- Chapter 23: Horcruxes
- Chapter 24: Sectumsempra
- Chapter 25: The Seer Overheard
- Chapter 26: The Cave
- Chapter 27: The Lightning-Struck Tower
- Chapter 28: Flight of the Prince
- Chapter 29: The Phoenix Lament
- Chapter 30: The White Tomb
We join Harry Potter as he enters his sixth year at Hogwarts. This volume is written from the point-of-view of the now 16-year-old Harry, as he takes advanced courses to prepare for the NEWT-level exams required for his chosen career. A darker book than the preceding volumes, it reveals more about Lord Voldemort's history and his impact on the Muggle world. Voldemort has emerged into the open, and his presence is beginning to have an effect on the day-to-day life of the Wizarding world.
While the series progressively covers seven years in Harry Potter's life, each of the first five volumes is largely self-contained. This book is written more as the first half of a two-part novel, and, as such, the ending feels rather incomplete.
Note: While this book is one of the longer ones in the series, at 607 pages (Bloomsbury / Raincoast edition), it is also set in significantly larger type. If it were the same size type as Harry Potter and the Philosopher's Stone, it would be 414 pages (approximately) to 223 for Harry Potter and the Philosopher's Stone.
- New places visited: Muggle Prime Minister's office (Number 10, Downing Street), Spinner's End, Marvolo Gaunt's residence, an orphanage in London, the cave where young Tom Riddle tortured two children from his orphanage (Dennis Bishop and Amy Benson), Fred and George Weasley's joke shop: Weasleys' Wizard Wheezes, Hepzibah Smith's house.
- Defence Against the Dark Arts teacher: Severus Snape
- New teacher: Horace Slughorn
- Title refers to: previous owner of Harry's borrowed Advanced Potion Making book.