Tyler Cowen thinks we should put down bad books:
[Cowen] finishes one book for every five to 10 he starts. "People have this innate view it comes from friendship and marriage that commitment is good. Which I agree with," he says. That view shouldn't, he says, carry over to inanimate objects. It's not that he's not a voracious reader he finishes more than a book a day, not including the "partials." He just wants to make the most of his time. "We should treat books a little more like we treat TV channels," he argues. No one has trouble flipping away from a boring series.
Finishing books has a lot to do with sunk costs. If a reader paid $25 for a book, it's a lot harder for them to put it down after ten pages than if a publishing house sent you a free review copy. That's why e-books make more sense. They cost less and so the investment is lower.
By the way, I think the same principle should apply to meals. If Americans simply left half their food on the plate, most of our obesity issues would disappear.