Mac OS X: We've featured two digital comic book readers before, but if you're looking for a full-featured library, look no further than ComicBookLover, which organises your library and allows reading with the Apple remote or with a laptop in portrait mode.
ComicBookLover's interface is remarkably similar to iTunes and provides many ways to organise your library. You can edit tons of metadata, put books into playlists and smart playlists and even search through them with spotlight. The coolest part, though, is the reading: Not only can you sit back and read books with your Apple remote, but if you have a laptop, you can turn it sideways and ComicBookLover will automatically adjust the pages for you using the accelerometer — perfect for reading it just like a real comic book. It supports the popular CBZ and CBR formats, as well as PDFs and folders of images.
ComicBookLover is a free download for Mac only. The free version has a watermark in the corner of the screen (which is usually pretty non-intrusive); the full version costs $US25. There are also early (read: unfinished) versions available for iPhone and iPad.