Harry Potter and the Half-Blood Prince is considered to the penultimate novel of the series. It also signifies the sixth year of Harry at Hogwarts. The novel discovers the past of Lord Voldemort and the preparations of Harry and his mentor Dumbledore for the concluding battle. It was in July 2005, when the book was released in United States, United Kingdom and other countries. In the first day of its release, nine million copies were sold.