"Harry Potter and the Deathly Hallows," the seventh and final book in the wildly popular the Potter series, went on sale today in anticipation of its July 21 debut.

That spells good news for Amazon.com. Chief Financial Officer Tom Szkutak said the company's "Deathly Hallows" sales today were up more than 200 percent in the first seven hours when compared with the first full day of sales for "Harry Potter and the Half-Blood Prince."

The online retailer has more reason to be hopeful: Amazon customers pre-ordered 1.5 million copies of the "Half-Blood Prince" before it debuted in July 2005.