At MagicBlox, you don't actually buy digital books.  You buy Access Passes for a very small monthly or yearly fee and you can read the books online or on your tablet devices.  If you want to purchase a physical copy of the book, some of our authors & publishers provide links to their own web sites or distribution partners where you can purchase a paper copy.  Clicking the "Buy" button on any book will take you to the link they provide.