First thing first, Proceeding on the assumption that Amazon speaks for itself and not on behalf of the entire industry, my response is, "Who cares?" It's a trend, and you're all arguing about how much is in the glass as the pitcher is still pouring. It not quantifiable, but it is a reliable indicator, and eBooks are becoming more prevalent and will continue to do so, and probably will do so exponentially at some point, if they're not doing so already.
As to which formats are used; again, I say, "Who cares?" If I'm selling a book and want to sell it as an eBook, I simply have a formatting service create files in the several various formats, and then sell the books at Amazon (Kindle), and iBooks (Mac format), and all the others (such as B&N) use EPUB. There's Smashwords too, but it's getting a bad reputation for a poor finished product. No matter what, everbody can use what they want, and any author can sell his or her books in that format. It's easy.
Most sellers and formats are trying to create library access programs as well. If you want it, give it time. It's going to be sold in your preferred format soon. And like movies, it'll soon be out on eBook as soon as the paper version is published. In fact, that time is already here, as I recently bought an eBook on the day of the paper print book release.
~ Jim ~
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