I tried fbkindle and it's quite nice. A much better ePub display than duokan.
It does seem to be missing spacing between paragraphs, so things look a bit crowded. Also the book list is too busy and I don't get the redundancy. Each book takes three lines. You have a choice to show/hide book, which just makes an additional 3 line entry. The original firmware and duokan both have much nicer and more usable book list.