Calibre is a powerful and easy to use e-book manager
Tusi Faitau Torium
Thorium Reader is an easy to use EPUB reading application.
MComix3
MComix3
CoolReader
Cross platform open source e-book reader.
Foliate
A simple and modern eBook viewer
Bookworm
Read the books you love without having to worry about different format complexities like epub, pdf, mobi, cbr, etc.