The seventh and final book in J.K.Rowling’s Harry Potter series book, “Harry Potter and the Deathly Hallows” has become most popular book as it broke a single-day global record at Borders Group Inc., the second-largest chain of book sellers in the United States, it sold 1.2 million copies worldwide. The book went on sale last Saturday, July 21, 2007. “This is the highest single-day sales of any title ever in Borders history,” Borders said.

Borders was selling the latest book for $20.99, a 40% discount from the $34.99 list price.

The six published Harry Potter books, “Harry Potter and the Half-Blood Prince” have sold around 325 million copies worldwide in 2005, Borders itself sold 850,000 copies worldwide during its first day of sales.

Rowling is known as the first-ever dollar-billionaire author. The books have also spawned a successful film franchise, with the first four installments earning global ticket sales of around $3.5 billion.

Fans have to line up outside bookstores around the globe as early as July 20, 2007 for a copy of “Harry Potter and the Deathly Hallows”, the seventh and final volume of the series written by J.K. Rowling, to complete all the seven Harry Potter series book.