It’s a clear and well written, and gives a well constructed theory of how and why communities form in or around things like Wikipedia, MeetUp and the Linux kernel.
Through the use of case studies, Shirky builds up a convincing framework of three elements: the promise of what the community offers; the tool which sets the environment for the community; and the bargain between the users which sets the rules of engagement. He also points out that the patterns of behaviour we see today have been emerging for quite a long time.
If there was a weakness to the book, it was that Shirky labours the point a bit with his case studies; at times it feels like he’s repeating himself so as to make use of all the carefully researched examples. I don’t think that really detracts from the overall picture though.
I’d definitely recommend this book to anyone who’s interested in what makes the social web tick.