Amazon has announced a new twist on its Kindle book sales business: textbook rental for students.

The service will allow users to rent a book for between 30 and 360 days. Full pricing isn’t available but the cheapest option (presumably the 30 day rental) will start at around 20 percent of the printed edition.

While prices vary, that looks to mean an average of around a third of the price to buy the same title in Kindle form. Users will be able to extend their rental period, including by as little as a day (great news for slackers) and also have the option to buy the title outright if they wish.

At the moment there doesn’t seem to be any clear pattern as to which titles will be available for rent. However, Amazon’s guide to ordering gives an example of a book that’s $184.99 in hardback, $109.20 to buy on the Kindle, and a starting price of $40.54 to rent. That may indicate its targeting the market for particularly expensive books such as medicine, accountancy and law, where the potential savings really do add up.

As with all Kindle books, user are able to make notes “on” the pages of the books. These will be accessible on all devices (including PC, tablet and smartphone apps) and will remain stored after the rental period ends, though of course the user will need to buy or rent the title again to access the notes.

Rivals Barnes & Noble already offer digital textbook rentals, but these only work on a special PC or Mac application: the company says textbooks aren’t suitable for reading on its NOOK device or smartphones.

There certainly should be a market for the rentals: various surveys across the past few years suggest textbook prices have risen far in excess of inflation, with the average annual cost to students approaching a thousand dollars. Since 2010, textbook publishers have been banned from selling books bundled with workbooks or multimedia discs unless they also sell the textbook alone at a cheaper price.