My predilection for printed books and manuals stems from over fifty years of conditioning. It’s not easy to change overnight, but I’m managing in the case of manuals. Novels however I still want in paper, I’ve noticed I have a much greater tendeny to yawn and even fall asleep reading e-Literature on a reading device than when reading the same from a book. Tried all manner of settings, contrast, background light, fontsize, etc. etc. For long periods of reading for pleasure, nothing like a book for me.