The Wisdom of Crowds: Why the Many Are Smarter Than the Few and How Collective Wisdom Shapes Business, Economies, Societies and Nations by James Surowiecki

I'm not sure why I started to read this book, since I'd already absorbed the bulk of it through osmosis since its concepts have permeated the Net-geek community that last couple of years. Still, I'm glad to have read the actual source.

As for the thesis of the book, that groups with the right attributes can consistently make better decisions than even the smartest individuals, it's spot on. And the book piles on evidence (both scientific and anecdotal) to support this. Go crowds! In fact I'll have a blog post coming up soon that goes into how I think this will shape an upcoming trend in web applications.