Rentals are listed as 80% off the retail price for hard copies and can be rented from anywhere between 30 days up to a full 360 days and used on your Mac, Kindle, iOS device and other mobile devices.
Here’s all the details straight from Amazon:
Kindle Textbook Rental is a flexible and affordable way to read textbooks. You can rent for the minimum length, typically 30 days, and save up to 80% off the print list price. If you find you need your textbook longer, you can extend your rental by as little as 1 day as many times as you want and just pay for the added days.
• Download one of our free Kindle reading apps for your PC, Mac, iPad, iPhone, Android device, Windows Phone 7, Blackberry, or Kindle – wherever you’d like to read your textbook.
• Search for your textbook in the Textbooks Store or from the search bar. If a Kindle edition is available for rent, you’ll see an option in the Formats section on the textbook page. Select this option.