Overdrive eBook titles (either ePUB, PDF DRM or MobiPocket eBook) require either Mobipocket Reader or Adobe Digital Editions to both view and download. However, there is another software application for reading a non-DRM e-books (such as the Gutenberg Project ebooks) on the Apple iTouch, iPhone or iPad.
Stanza is an ePub software reader and converter that is fast, light-weight, and simple. It provides a highly customizable reading experience, with the ability to quickly change text size (with a slider in the settings, or using pinch and reverse pinch), adjust line and margin spacing, bookmarks, and choose from many different fonts. It is a free application available at the iTunes store.