One man's killer app is in another man's garbage bin.
You can have all the bells and whistles you want, but personally I would rather have a simple reader that integrates into the file browser. I would much rather sort my own books in my own folder structure than rely on the programmers taste in "bookshelf" building.
Concentrate on getting the book to display correctly first. Once you have that licked, then you can write your bookshelf wrapper around that, just leave me the option to ignore it if I need to.