Calibre is an open-source, full featured, ebook library management and reading software available in Mac, Windows and Linux platforms. It also works as a portable application that you can install and run from your USB storage device. A new version, Calibre 0.8.61, has been released which features a new paged mode that will make reading ebooks easier.
Calibre features library management tools that allow you to view, sort and edit ebooks according titles, authors, date added, date published, etc. It has a powerful ebook conversion feature which can convert ebooks from one format to another. The converter allows rescaling font sizes, creating book structures and table of contents. You can also use Calibre to sync ebooks with your other devices like mobile phones, ebook readers etc and download news from web and convert it to ebook format.
You can install Calibre 0.8.61 in your Ubuntu based distro by issuing the following commands
sudo add-apt-repository ppa:n-muench/calibre
sudo apt-get update
sudo apt-get install calibre