Samsung Galaxy Tab S 8.4 with the adaptive display on is just better than any book IMO. The lighting is always perfect, the text is clearer than paper.
I will be heart broke then I eventually have to replace it. To do anything but read on it is a sin.
Reading on paper, I am just slower than reading on the S 8.4.
2560x1600 on such a small screen is what is needed to beat paper.