Moving this discussion to the Adobe Digital Editions forum.
Siobhan please see View e-books | iOS, Android devices - http://helpx.adobe.com/digital-editions/kb/view-e-books-ios-android.html for information on how to view your content on iOS.
The iPad doesn't seem to be on that list. I have looked several times and can't find it. Any further clues?
Siobhan the iPad runs iOS. So any of the offerings for iOS will work on the iPad.
For library books, install the Overdrive app on the iPad; that can borrow, download and read Overdrive library books (as used in many countries).
For other DRM .epub books, install the Bluefire app on the iPad.
Install ADE on a PC/Mac, and make sure your ADE and Bluefire are registered with the same AdobeID.
Download .epub books to the PC using ADE and then copy them to the iPad and read with Bluefire.
Unfortunately, Apple likes to make what should be a simple copy operation difficult; so you have to copy indirectly, for example using iTunes, Dropbox or by emailing to yourself.
I am having the same issue - no matter what i use (ibook, bluefire) I cannot download an epub book - I get an error that Safari cannot do this or an unknown error - brand new ipad mini - any hints? So far, I'm finding I like my android tablet MUCH BETTER!