Perspectives on Free and Open Source Software – an influential collection of essays with an influential collection of contributors – now updated and available as a PDF download, or for purchase. The individual chapters can be downloaded too – handy.
Peers, Pirates and Persuasion – John Logie’s book on rhetoric in the peer-to-peer debates. I’ve only read the first bit, but it’s a very interesting look at what’s normally discussed as a pure legal issue. CC license, too.