When you think of digital books, I'm sure Amazon's Kindle and Apple's iBooks come to mind. Both are good sources for digital textbooks, and as you already know, the services are compatible on a wide range of devices. Amazon will let you "borrow" a book for a desired length of time whereas you have to purchase a digital copy outright from Apple.
Another good options is eCampus.com. The site claims to carry over 100-thousand different titles that are available for purchase or rent. The service lets you share information with other users and access through apps on your iOS or Android devices.
Inkling is another website that syncs with your mobile device and offers hundreds of textbooks, especially in the business and medical fields. Readers will enjoy the easy to navigate site.
Of course, be sure to check with your teacher or professor to make sure he's ok with digital copies and triple check to make sure you're purchasing the correct edition.
(Kara Tsuboi, CNET.com for CBS News)
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