via pdroms

This application allows you to read large Text (.txt,.text), Palm Doc (.pdb), Mobipocket (.pdb,.prc,.mobi), Plucker (.pdb), HTML (.htm,.html), and Fiction Book (.fb2) files quickly and efficiently on the iPhone/Touch. This application doesn't have the fancy formatting of ruBooks or Books.app, but it can quickly load and display large text files that currently cause Books.app or other UI Text View/Web View based apps problems. If you want to load books quickly and read text, this may be the app for you.

Note: Books.app http://code.google.com/p/iphoneebooks/ and ruBooks http://colel.info/rubooks/ provide a formatted display of text and images. If you are willing to break up your book into smaller chapters they may also be options. http://code.google.com/p/iphonetextreader/