I use my rooted nook color (CM7) to read mangas. I use two apps, Perfect Viewer and Manga Watcher.
Perfect viewer is what I use for CBZ/CBR files and it has custom zoom and bookmark functions.
http://www.appbrain.com/app/perfect-....perfectviewer
Manga Watcher is an app where you can read your mangas straight from its supported manga websites or download them from those sites and read offline. You can also open your sideloaded mangas. It has the basic functions like pinch to zoom, bookmarking and landscape/portrait mode.
http://www.appbrain.com/app/manga-wa....mangawatchman