I used Mobipocket and Fictionwise quite a bit many years ago when I read books on various PDAs. That was of course before the eInk reader and smartphone eras. I'm not sure how my eyes ever focused on words for very long on those old 160x160px square Palm Pilot screens, but I managed somehow. Then one day they introduced 320x320px color screens...woohooo! Obviously we have come a long way in the past 15 years. I just hope screen technology keeps improving to counterbalance that my old eyes keep degrading.