ComicNerd is a comprehensive comic book reading and management app. It can be used to open .CBR, .CBZ, .RAR and .ZIP comics. You can simply drag and drop your comic book files to add them to your list. The application will automatically grab information from the file name of your comics, and it will display that information on your list. This can save you a lot of time that you would spend entering all this data manually. Once your comics are added, you can simply double-click them to open them in the viewer. When you do that, a new window will appear and your comic will be loaded. You can either use your Mac's trackpad or the arrow keys to navigate the comic. You can resize the window but there doesn't seem to be a full-screen mode, which is a lost opportunity. That would have been a great way of reading comics. The viewer is simple and quite fast. You can close it to go back to your comic book list.
I tested this app by loading a few of my comics and viewing them as I would normally do. I didn't detect any problems, but I have seen some complaints of users who are having problems importing their comic book collections. Since I don't have a big collection, I couldn't try this.