"Free: The Future of a Radical Price" by Chris Anderson. It's about how free is used in business models, how it affects the economy, about people who simply give away things for free (and how it affects the economy), and to some extent- how you could use the idea of free in a business model to make money yourself.
I wish I had access to better libraries though, as it stinks when there are books you would love to read but your library doesn't have them.