ComicRack supports cbr(rar)/cbz(zip) and pdf files. But there are some pitfalls.
ComicRack expects that the extension really matches the content. So if you have a cbr/rar file but it has a cbz extension, you will not be able to view it and no thumbnail will be shown.
Pdf support is very hacked together. ComicRack only searches all images embedded in the file and displays them as pages. This can lead to funny results with some pdf files :)