The interesting aside here is the other digital venue of podcasting. Having created podcasts myself in the past, and shifting now to the consumption side of the equation, I find myself reading more eBooks than hard cover, but wishing there were good audio books along the lines of podcasting. For me Audible has been hit and miss, so the reason I am into eBooks (specifically Kindle) is due to the lack of other reliable consumption methods digitally.
So:
1. eBooks (Kindle)
2. Audible books
3. Real books
So:
1. eBooks (Kindle)
2. Audible books
3. Real books