K. Rowling's seven Harry Potter books, had more than 2, 700 sold-out screenings, according to MovieTickets.com.

CNN: Potter's 'Prince' sets midnight record

However The Casual Vacancy has failed to touch sales of Rowling's seven Harry Potter titles.

BBC: JK Rowling novel tops fiction chart

K. Rowling's website started selling digital and audiobook editions of all seven Harry Potter novels to English-language readers.

WSJ: What's News

All seven Harry Potter books combined have sold more than 450 million copies.

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Altogether the seven-book Harry Potter series has sold more than 450 million physical copies globally since it debuted in 1997.

WSJ: J.K. Rowling's Novel 'Casual Vacancy' Gets Large Print Run

In many cases, they grew up reading the books, and for the past 10 years they've watched the actors portraying Harry Potter and his friends grow up themselves in seven big screen adaptations from Warner Brothers.

CNN: Harry Potter and the morning after

In 1990, she had her Harry Potter inspiration, and began developing a detailed plan for a seven-book series.

NEWYORKER: Mugglemarch