From Daily Finance:
Say one thing about books in print: While there's a dizzying amount of choice, there's basically one format for pages: Paper. But the increasing popularity of electronic books means readers must not only navigate through hundreds of thousands of books online for the one they want, they must figure out whether it can be read on their favorite digital device.
In an ideal world, you could buy a digital book by a favorite author and then be able to read it on your Kindle (AMZN), your iPad (AAPL), your Nook (BKS), your BlackBerry (RIMM), your laptop or any other gadget of choice. You'd be able to transfer it between computer and smartphone and access the e-book anytime, anywhere and in any country.