The Kindle Unlimited service is available for $9.99 a month, and offers a library of more than 600,000 e-books and thousands of audiobooks.
The service works on Kindle devices, as well as Apple iOS and Google Android devices that have the Kindle app installed. It's only available to U.S. customers.
Amazon already hosts a Kindle Owners Lending Library, available to subscribers of Amazon Prime. However, as the name suggests, users must own a Kindle device to gain access.