Harry Potter is a series of seven fantasy novels written by the British author J. K. Rowling. The books chronicle the adventures of a wizard, Harry Potter, and his friends Ronald Weasley and Hermione Granger, all of whom are students at Hogwarts School of Witchcraft and Wizardry. The main story arc concerns Harry's quest to overcome the Dark wizard Lord Voldemort, whose aims are to become immortal, conquer the wizarding world, subjugate non-magical people, and destroy all those who stand in his way, especially Harry Potter.Since the release of the first novel Harry Potter and the Philosopher's Stone on 30 June 1997, the books have gained immense popularity, critical acclaim and commercial success worldwide. The series has also had some share of criticism, including concern for the increasingly dark tone. As of June 2011, the book series has sold about 450 million copies, making it the best-selling book series in history, and has been translated into 67 languages. The last four books consecutively set records as the fastest-selling books in history.A series of many genres, including fantasy and coming of age (with elements of mystery, thriller, adventure, and romance), it has many cultural meanings and references. According to Rowling, the main theme is death. There are also many other themes in the series, such as prejudice and corruption.