what they are is image files in a zip (cbz) or rar (cbr) files. They are siquential files. It would be just a image viewer that zooms in on the page. a good program is like CDISPLAY.
No it isn't. I've used the picture viewer for firmware 1.0 to read the Ocarina of Time manga without a hitch. (Remember, that has no zoom OR rotation) Although it was a little small text, if it was rotated it would've been perfect, and adding a zoom function only makes things easier.
You just don't have a manga addiction would be my guess. ;P