Amazon announced Thursday that it has launched the Kindle Owners’ Lending Library for owners of its e-reader who are also subscribers to its Amazon Prime service.

Prime members can borrow one book a month, with no due dates. Users are allowed to have one book out at a time, the company said in a press release. All notes, bookmarks and highlights made on the borrowed book will still be there if the customer later purchases or re-borrows the book.

The addition adds to the already enticing features of Amazon Prime, which includes free two-day shipping and unlimited streaming of the company’s 13,000 title catalog of TV shows and movies. That service costs $79 per year.

There is a catch, however: The books are only available on Kindle devices, which means that there will be no free borrowing for Kindle Apps users. (Unless you’re borrowing books from your local library.)

All of this comes in the run-up to the launch of the Kindle Fire on Nov. 15, a device that will deliver Amazon storefronts directly into the hands of thousands of customers. By continuing to add services to Prime and plugging the content holes in the service, Amazon is on the edge of locking even more customers into its retail ecosystem.

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