Alan Jacobs, The Pleasures of Reading in an Age of Distraction (Oxford University, 2011), 17:

For heaven’s sake, don’t turn reading into the intellectual equivalent of eating organic greens, or (shifting the metaphor slightly) some fearfully disciplined appointment with an elliptical trainer of the mind in which you count words or pages the way some people fix their attention on the “calories burned” readout—some assiduous and taxing exercise that allows you to look back on your conquest of Middlemarch with grim satisfaction. How depressing. This kind of thing is not reading at all.