Kevin of jkOnTheRun
tested two very popular free iPhone apps for reading e-books. One is
Stanza, the other is
eReader. His first impressions: Stanza looks prettier and pagination works better and quicker. eReader, on the other hand, has more theme options (background and text color).
One important difference is that Stanza supports various e-book formats, including those without DRM, whereas eReader uses exclusively the eReader PDB format (with and without DRM).
Related: Best ebook reader for iPhone?