I am about 1/2 of the way through Predictably Irrational and am really enjoying it. While I think much of the topics covered fall into the obvious/previously covered category, it is interested to be reminded at how predictably irrational we truly are.
The first chapter 'The Truth about Relativity' covers concepts I've known (I've been known to (over)use the term 'it's all relative'), but provides empirical evidence that really demonstrates how predictable irrational behavior is. It really puts 'keeping up with the Jones'' in perspective.
The second chapter covers the concept of an anchor price. Our perception of what what something is worth is based on our first purchase or near purchase of that item, again with some interesting experiments to support the ideas.
Chapter Three covers the cost of zero, or why we alter our behavior when something is FREE FREE FREE!.
Chapter Four is another chapter that rings true for me. The title is 'The Cost of Social Norms', IE when it is a bad idea to offer to pay your Mom for Thanksgiving dinner! But for me it reminded me of my experiences developing Open Source software, and how they changed when I got paid.
I could have read the book straight through, but I wanted to take a break so some of the ideas could sink in before continuing. It is amazing how much reading you can get done when you have a sick kid sleeping on your lap all day!