All seven books in the popular Harry Potter series is now available without cost or potential back aches from lugging around the dense books. The books are available through Kindle Owners' Lending Library. Fulfilling the promise it made last month when it announced a deal it had struck with J.K. Rowling's company, Pottermore, Kindle owners can now be assured an unlimited supply of the books. The books will never be checked out as popular print books can be at a brick and mortar library.

"Nowhere else can customers borrow any of the seven Harry Potter books for free, with an unlimited supply of each title and no waiting list," Russ Grandinetti, vice president of Kindle Content, said in a statement. 

The deal constituted a major investment by Amazon to offset lost sales to Pottermore."The way the deal is structured means that any lost sales are more than made up for," Pottermore CEO Charlie Redmayne said last month in an interview with PaidContent. "Yes, some people will borrow from the Kindle Owners' Lending Library and therefore not buy, but Amazon is paying us a large amount of money for that right, and I believe it's a commercial deal that makes sense." 

Customers can only borrow one book at a time but they also have the option of re-borrowing or buying the book, if they choose. The Lending Library is part of Amazon's Prime membership program, which costs $79 a year. Prime members can borrow one book a month for free, which includes 145,000 titles, some of which are New York Times bestsellers.