
The iPhone and iPod Touch are both compatible with Feedbooks for downloading and reading.
While it is technically possible to use PDF files on both devices, it's not exactly the best solution: Apple designed the software in a way that makes it impossible to save those PDF files on the device, and you'll have to create a custom PDF file to get a good reading experience.
Hopefully, with the release of the App Store there's now a much better way to experience Feedbooks on an iPhone/iPod.
Stanza by Lexcycle
Stanza is the first application using the new Feedbooks API. You can browse and download books from Feedbooks (ePub file format) directly from your device.
You can download this application on the iTunes App Store.
Here's the official description from Lexcycle:
“Read electronic books on your iPhone and iPod Touch! With a reading interface that is unprecedented in its clarity and ease of use, Stanza is bringing the eBook revolution to your pocket. Store and categorize hundreds of books in the organizer, choose from thousands of free books available in the Lexcycle Online Library, and transfer books you share from your computer using Stanza Desktop. Your entire summer reading, your class syllabus for the whole year, or all the reference material you will ever need: all at your fingertips. Literally.”
Browsing and downloading books once you've installed Stanza is very intuitive, just select Online Catalog and Feedbooks to get books from our service: