Review: The Cathedral & The Bazaar
First, it helped inspire me to try Linux, which is no mean feat for a die hard Windows guy like me. (I haven't even turned on my iMac in the last year.)
Second, the management essay added at the end was the most important part to me. The main point being that OSS works well because the participants self select and are passionate about that they are spending their precious time on. Cube dwelling devs may not be so passionate or skilled, and their output reflects that.