If you are interested in social computing, collective action by groups, sociology of groups, and group dynamic, then this is the book for you. Download his podcast from BusinessWeek.com.

This book is clearly written, succinct, and relevant and current of the technologies we use today. Each chapter is composed of a story to demonstrate the psychological theories, but the difference, these aren't controlled experiments from the 60's (residue from my undergrad studies in psychology). Reading the first chapter reminds me of Malcolm Gladwell's Tipping Point, basically comprehendable to lay people like me.

Anyway, I'm a little biased because I had Clay Shirky as a professor twice.