Amazon has confirmed the details of its Kindle “lending library” for Amazon Prime subscribers. It’s a neat feature, though not enough to be the sole reason to subscribe.

The library of books available to “borrow” is around 5,000 titles of which more than 100 are either currently on the New York Times Bestsellers list or have been in the past.

There’ll be a separate “library” to browse, but eligible titles will also be marked as having a borrowing option when they appear in standard search results.

The deal works a little like the basic package of most DVD and game rental services. You can borrow one book at a time and keep it as long as you like. Once you “return” it you get a new one, but you can only get one new title a month.

The feature is available on all Kindle devices, including the new Fire tablet. However, the borrowed books can’t be read on non-Amazon devices through the Kindle app in the same way as purchased titles.

A year’s subscription to Prime is $79, so if you used it just for the books you’d be talking about $6.50 per title. Given bestselling titles average about ten bucks, that’s a lot for borrowing a book, though a bit more tolerable if you rarely read books more than once anyway.

Throw in the unlimited TV and movie streaming, however, and you’ve got an attractive deal for those who’ve opted for the Fire tablet, giving more weight to the theory that Amazon isn’t planning to make its money on the hardware but rather the content.