What I don't understand is why no one has developed a great ePub reader for iOS, Android, MAC OS, Windows, Linux, etc. Even if we had to pay $9.99 to purchase it, it would be worth the money. Instead we have dozens of half-a$$ed apps out their and none of them are really close to being great. Way back when I used PDAs on a daily basis, way before the smartphone/tablet era, we had several good readers for PalmOS and Windows Mobile devices. Some were free and some were for pay, but many of those were far superior to anything available today on any platform, IMO. It has been too long to remember the app names now.
The big bookstore companies turn out lackluster reader apps. I'm talking about Apple, Amazon, Sony, B&N, so there is a huge market there for developers to produce better apps for ePub and mobi, but none have yet to produce an app that is really that much better than the BIG EBOOKSTORE companies.