Which is NOT a book in the Harry Potter Series?

The story behind the answer

The House Elf is not one of J.K. Rowling’s seven main Harry Potter novels. The other options—The Chamber of Secrets, The Prisoner of Azkaban, and The Deathly Hallows—are genuine titles. House-elves (like Dobby and Kreacher) are important magical creatures in the series, but they never headline a book.

The core series includes: Philosopher’s/Sorcerer’s Stone; Chamber of Secrets; Prisoner of Azkaban; Goblet of Fire; Order of the Phoenix; Half-Blood Prince; Deathly Hallows. Memory trick: “Stone, Chamber, Prisoner, Goblet, Order, Prince, Hallows” (S-C-P-G-O-P-H). Companion books such as Fantastic Beasts and The Tales of Beedle the Bard expand the world, but they’re not part of the main seven.