If the brain is predictably irrational, then the books which warn us we aren’t the rational creatures we hope are also predictable. I don’t think there was a single circumstance in Ariely’s book I wasn’t already aware of from one experiment or another, one summary or another. That said, Predictably Irrational is well written and easy to digest; there’s no technobabble, and everything is presented in a very readable and readily understandable format. It’s not Dan Ariely’s fault that I’ve read all this stuff before.
If you don’t know much about the topic of the way our brains work, and how counter-intuitive it sometimes is, then this is a good place to start. Unfortunately, that means I don’t have much to say about it — it didn’t hold any surprises for me.