I am testing the ePub firmware on my Gen3 and looked at this book. There are some problems:
The top margin is too small. The text is cut by the black "border" or if not cut it is so near that it looks to be cut and also the shadow when reading can be one line thick so you need a top margin.
I cannot disable justification.
The body font has high x-height so I think you need more leading. Also with a reader with no hyphenation and justified text the lines are to close to each other.