Eeek! I'd have to answer this question by saying that I probably read about 4 to 5 ebooks a month on my Thera. We're not allowed to be reading for obvious reasons at work and our screens are captured while we're working with customers, so I charge up MS Reader all day long.
I usually have the paper copies of the same books at home but lately found myself kicking back on the couch with my PPC rather than expending the energy turning pages. *grin*