Some time ago, Apple introduced the ability to purchase textbooks through the iTunes store as well as a tool that allows pretty much anyone to publish interactive books:

http://www.apple.com/ca/education/ibooks-textbooks/
http://www.apple.com/ca/ibooks-author/









Today, Google is announcing:
(http://www.engadget.com/2013/07/24/google-play-textbooks)