best ubuntu e-reader

[Albert Wagner]

http://en.wikipedia.org/wiki/Comparison_of_e-book_formats

What reader you prefer depends on what you want to read.  Older kindles, 
like my paperwhite, use Amazon's .azw format, which is proprietary.  I 
assume that kindle's newer format, kf8, is also proprietary.  Decide 
first whether you need to read recently published copyrighted works or 
publicly available stuff.