Boundless is a a new service that offers alternatives to pricey textbooks along with study materials. Start by choosing your subjects or searching for your required textbooks. Boundless then offers alternatives that you can buy as an in-app purchase. The iPhone app then let you take your material with you everywhere.
As far as selection goes, I was able to find updated editions and alternative books for almost all the accounting and tax books I had sitting around from college. Boundless had alternatives for most of them along with supplemental study materials including flashcards and quizzes.
You can use Boundless either right on your iPhone through the native app or by logging in to their website. If you're looking to save some money on textbooks, users of Boundless seem to think it's a pretty good service. They also offer a money back guarantee so if you drop a class or aren't happy with the content, you have 30 days to get the money back you paid for textbook alternative.
Buying a book from Boundless will cost you $19 for each one. If you would rather use your actual textbooks, Boundless can still provide great study material across many different subjects which makes it a great resources whether you use their alternative book service or not. Their free open Boundless books section lets you view information on many topics without paying. You only need to spent the $19 if you want the study materials attached to their collection of books.
If you've tried out Boundless already, let us know what you think of it!