Kelly Jane Torrance has a very good article on this question. This part is quoting yours truly:
"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
There is more:
"If I'm reading a truly, actively bad book, I'll throw it out," he
says. His wife will protest, but he points out that he's doing a public
service: "If I don't throw it out, someone else might read it." If that
person is one of the many committed to finishing a book once started,
he's actually doing harm.
Mr. Cowen, who says he couldn't finish Alexandre Dumas' "The
Three Musketeers" or John Dos Passos' "U.S.A.," offers a more direct
economic rationale. He notes that many up-and-coming writers complain
they can't break through in a best-seller-driven marketplace. "We're
also making markets more efficient," Mr. Cowen says. "If you can sample
more books, you're giving more people a chance."