An good little .cbr comic book archive reader for Ubuntu (or for any other Linux distro at that) is Comix, a lightweight and free image archive viewer by Pontus Ekberg, a computer science student from Sweden.
It has all the normal stuff (as well as a ton more) that you would expect from a comic book reader, including:
- Fullscreen mode.
- Double page mode.
- Fit image to window width, height or both.
- Rotation and mirroring.
- Magnifying glass.
- Image enhancements.
- Both left-to-right and right-to-left reading modes.
- Bookmarks support.
- Archive comments support.
- Archive editor.
- Comic book library.
- Reads most common image formats.
- Reads ZIP and tar archives natively, and RAR archives through the unrar program.
- Runs on Linux, *BSD and virtually any other UNIX-like OS.
It is easily added to your Ubuntu installation by a simple search and install on the term “comix” via your Ubuntu Software Center.
Related Link: http://comix.sourceforge.net/