Free Software Free Society: selected essays of Richard M. Stallman (GNU Press)
Free as in Freedom: Richard Stall's Crusade for Free Software by Sam Williams (O'Reilly)
Free Culture by Lawrence Lessig: How Big Media Uses Technology and the Law to Lock Down Culture and Control Creativity [Hardcover | 5.00 x 7.51 in | 348 pages | ISBN 1594200068 | 25 Mar 2004 | The Penguin Press] (full text available online)