Your iPhone 3 or iPhone 4 reads the following formats: ePub and PDF.  Most of the C.O.D. Library's e-book collections are available in PDF format. 

The Library has some books that can be downloaded in ePub format available through the EBSCO E-book platform.  Search this collection and look for "Download (offline)" to check out the book to your iPhone. You will need to install the Bluefire Reader app to read ePubs from the library on your iPhone. 

Many public libraries have e-books available for download to your iPhone.  Please contact your public library for more information. 

For more help with your iPhone, go to the Apple iPhone Support page.