On Linux, I rename epub to zip, unzip it and use browser to read books.
If you don't already know about Calibre, I wholeheartedly recommend it.
You don't even need to load the books into calibre's database to view it. You can invoke 'ebook-viewer' from the command line directly with the epub file's path as the argument.
There's even a console reader, if the reason for unzipping is reading in the text terminal: https://github.com/wustho/epy