I tried a few comic book readers (including free ones) but this is one of the best for its price. It is specially designed to read Japanese manga because the author of this app is Japanese.
Note that this app doesn't find comics for you so you'll have to find and download them yourself. (For another app that does that, please read the End Notes below.)
Features include:
- Supporting .zip and .cbz formats without the need to unpack them. Otherwise supports JPG, TIFF and PNG.
- Transfer comic easily via FTP connection through WIFI network.
- Easily navigate and flip pages using hand gestures.
- Zoom feature works well.
The app doesn't have a free version and it costs $0.99 at the time of writing.
End Note:
Manual for setting up iComic can be downloaded here: http://red.halfmoon.jp/AppStore_iComic_V1.3_FAQ.pdf
For those who have no idea where to download mangas, I recommend another app which is just as good in terms of reading manga, plus it finds and downloads manga directly to your iPhone. If you want a decent Manga Downloader + Reader, have a look at Mangashelf.
Screenshots: