John Herrman has nice counterpoint on the rise of ebook apps, underscoring that quantity is not the same as quality:
Treasure Island, a free, public domain book, is available for purchase as a standalone app from over a dozen different developers, in all kinds of containers, at all kinds of prices. And why not! the content is free, so once developer has designed an ebook app container, he can just paste any public domain etext in there and throw it into the App Store. I have no idea if these things sell, but to be honest, they wouldn’t have to do very well to make money for their developers—the investment is minimal.