Welcome to the EPUBReader forum!
EPUBReader is a Firefox addon with which you can read ePub-files just in Firefox. For installation, please go to the Mozilla addon website: https://addons.mozilla.org/addon/45281
Here you find more information about EPUBReader: http://www.epubread.com/
If you have got problems or ideas how to improve EPUBReader, please open a new thread in this forum.