Kindles can actually read comic books, and it works with the alternative Duokan firmware too (awesome piece of software, you should use it). You just have to rename the CBZ files to ZIP. But sometimes the pictures might not be in the right orientation, as they would be easier to read in landscape instead of portrait, and files are heavy with high resolution images we don't actually need on the Kindle screen.
So here is a short and useful script to convert a CBZ, ZIP or CBR comic file to a Kindle-compliant ZIP file: cbz2kindle.sh
Usage is easy:
$ cbz2kindle.sh My_Comic.cbr Unraring... Resizing, trimming and converting images... ............................ OK Re-zipping to My_Comic.kindle.zip...
You will need imagemagick, unzip and rar (part of the Debian non-free archive) to make this work.
The script is actually converting JPEG files to PNG while rotating them to fit best, resizing to 800x600 and converting to a 16 levels grayscale image.
Its works quite well with some comics, and the size is small (around 25MB for a 300 pages comic book). But some comics are intended for a larger format and the text is hard to read sadly. We really need a 12"-something color e-ink e-reader really. Where is it?!