This collection of essays by FSF founder and president Richard M. Stallman is a thorough primer on the free software movement. Learn about free software ethics, licensing, and how the movement views particular problems.
A .pdf of the book is available at http://www.gnu.org/doc/fsfs3-hardcover.pdf, and the source is http://www.gnu.org/doc/fsfs3-hardcover.tar.gz. The cover art can also be found at http://www.gnu.org/doc/fsfs3-hardcover-cover-art.svg.
Reader Andreas Heil sent us this hack for the .pdf edition: To generate a copy of the book that enables you to open an interactive table of contents using a PDF reader, in scap.texi, replace "@shortcontents" with "@contents". (Please note that this will affect both the appearance of the table of contents and the page count.)