Amazon.com Inc. continues to add to what subscribers to its Amazon Prime program get for their $79 annual membership fee. The e-retailer today announced that consumers who subscribe to Prime and also own an Amazon Kindle e-reader or Kindle Fire tablet computer can borrow e-books to read on those devices as part of their membership.

The company says the Kindle Owners’ Lending Library includes 5,000 titles from a range of publishers, including Amazon’s own imprints. Kindle owners who participate in Prime can borrow one book a month at no cost. Consumers can keep the book on their Kindle devices for as long as they like provided they do not borrow another. When consumers want to borrow another book, they have to return the previous book.

Amazon launched Prime in 2005, offering free two-day shipping on all Amazon purchases in exchange for a $79 annual membership fee. It added free access to Instant Video, Amazon’s video streaming service for movies and TV shows, to Prime subscribers earlier this year. Amazon has steadily signed agreements with movie studios and TV networks to add to the content available in its Instant Video library. At launch in February it had 5,000 titles available to Prime subscribers; it now has nearly 13,000. 

Amazon says it expects the lending library will help business. “We expect three immediate results: Kindle owners will read even more, publisher revenues will grow and authors will see larger royalty checks,” says Russ Grandinetti, vice president of Kindle content.

Amazon says it has reached agreements with publishers to include titles in its lending library for a fixed fee, but did not disclose what that fee is. In some cases, Amazon says, the e-retailer is buying the title each time a Prime member borrows it under standard wholesale terms. Amazon says it will demonstrate to publishers that they can ultimately grow sales through the free lending service, as Amazon has with movie and TV studios with Instant Video. “With the growth in Prime membership and the recent addition of Prime Instant Video, we’ve been able to broaden our relationships with movie and TV studios and significantly increase their revenue,” Grandinetti says. “We’re excited to expand that investment to books.”

Amazon does not say how many Amazon Prime members it has, however investment analyst Herman Leung of Susquehanna Financial Group this summer predicted that about 15 million consumers will belong to Amazon Prime by the end of the year. Amazon.com is No. 1 in Internet Retailer’s Top 500 Guide.