It seems journalists are having some trouble in coming up with a concise term for 'enhanced ebooks', e.g.:
E-Books Fly Beyond Mere Text
The Two Minds of Amazon on eBooks
Let's help them out.
I propose the following acronyms/terms:
MEB - 'multimedia electronic book'
or perhaps
MEEB - 'media enhanced electronic book'
'meBook' seems to be taken already and is maybe too cute.
'electronic' is preferred to 'digital' because a vowel is required to make a pronounceable acronym that could morph into a real, uncapitalized new word that eventually you could use in Scrabble play (my hidden agenda

).
In any case I would make a distinction between enhanced ebooks that leverage existing ebook formats like ePub or mobi, and those that leverage multimedia platforms like Flash, or HTML5 (not to mention specific OS platforms).
But surely there are other possibilities? Let's hear your ideas!