Stanza is a application in the App Store that will allow you to read eBooks on your iPhone and iPod Touch. What’s so special about this ebook reader? Well it’s got wireless syncing, swiping or tapping to switch pages. You can edit the txt sizes and it has desktop apps for just about every os out there.
» App Store – Stanza (iPhone ebook reader)

RuBooks is a enhancment of the Books application.
Rubooks can open OC/PDF/XLS, FB2, including support to zip-archived files.
I has localization support for Russian, German, Chinese, English and Japanese.
With rubooks you can search Texts, scrool with the volucom buttons, has support for table of contents, book cover and you can virtually open any book file anywhere on your device.
Overall this app is a good improvement over the old books app :)
» RuBooks

I must admin that your iPhone or iPod Touch may seem a little small to read e-books.
However the app Books does do a pretty good job for reading e-books.
The app is a simple eBook reader and can read html and texts stored in your ~/Media/EBooks folder.

Getting Books? Books.app is recommended for use with Project Gutenberg texts,
in conjunction with GutenMark, a fantastic PG markup tool by Ronald Burkey,
which makes pretty HTML out of Gutenberg .txt files, and splits them by chapter using a second tool.

I”ll explain with screenshots..

» Read your e-books with Books