This WILL happen for books. IN fact in some ways it is already starting to happen. The key is forming communities of interested audiences. It’s nicely put by Eric though:

The reason this works anyway is that radio has large fixed costs and infinitesimal marginal costs. If the listenership doubles, the costs stay exactly the same. It’s not like book publishing, which spends a lot of money pumping paper through a complex supply chain.

A book can cost a lot to produce, too. An author might devote a whole year to the writing of a book. Let’s be generous and say the author deserves $200,000. There’s an editor, a graphic designer, maybe an illustrator who also work on the book. Add some management overhead, tax accountants, lawyers, and it’s easy to get over $300,000 in fixed costs, and we haven’t even started promoting, printing and shipping the book. Many books, of course are produced for much less money. Some authors don’t get paid a cent.

via Go To Hellman: The Public Broadcasting Model for eBooks.