If the last mile of a truly comparable e-book reading experience is the user interface, I think solving that has more to do with understanding how we read than how to deliver documents. What do we really want to do with the e-book? Highlight, underline, annotate in the margins? How would we measure the utility of flipping through pages? What about the tactile context of always knowing where you are by feel? Are there measurable cognitive differences between the two media? A quick google search suggests that perhaps the answer is yes – “Results show that the e-book presence hinders recall of assimilated information whilst the presence of the paper support tends to facilitate it.” (http://dx.doi.org/10.1016/j.ijhcs.2004.10.002)