Merlin's beard! Ever since Harry Potter and the Sorcerer's Stone was published in 1997, each subsequent Harry Potter novel released in the U.S. has broken the sales record of the one that came before. The seventh and final entry in the series, Harry Potter and the Deathly Hallows, was a landmark moment for British publishing, as 12 million advance copies were printed in the States alone, more than have been printed for any other book sold through Amazon and Barnes & Noble. Critics believe the key to the global success of J.K. Rowling's series has been its popularity in the U.S., where more than 1 in 4 Americans over the age of 12 claims to have seen a Potter movie. The books have been translated into 65 languages, with publishers everywhere trusting that if the formula works in the U.S., it can't be wrong.