Which Harry Potter novel by J.K. Rowling was the fastest-selling book in publishing history at its release?

Harry Potter and the Deathly Hallows was the fastest-selling book in publishing history at its release. The seventh Harry Potter novel was published worldwide on 21 July 2007.

It sold more than 11 million copies in the United States and the United Kingdom during its first 24 hours, according to contemporary publisher figures. The book concludes Harry’s struggle against Lord Voldemort and answers major questions established throughout the series.

The record is about the book’s launch performance, not the total lifetime sales of every Harry Potter title. Earlier installments had also broken sales records, especially Harry Potter and the Goblet of Fire, Harry Potter and the Order of the Phoenix, and Harry Potter and the Half-Blood Prince.

The novel was adapted into two films, Harry Potter and the Deathly Hallows – Part 1 and Part 2. The two-film adaptation explains why the film franchise contains eight movies even though the main novel sequence has seven books.