I quite enjoyed Predictably Irrational, though it wasn't quite what I was expecting. This is a better book, though again in part for unexpected reasons.
First up, it's actually quite a personal book. Part of Ariely's pitch is to remember our humanity, particularly in the face of policymakers who assume we are rational, self-interested maximisers. He draws a bit on his own experiences, in particular the very nasty accident that he suffered as a teenager, to point out where biases kick in and how they affect us. The result is a popular book about behavioural science that has a very human feel to it, and that makes it a nice read.
Secondly, as with Predictably Irrational, Ariely has some genuinely interesting and innovative experiments to talk about. The two most interesting bits of research for me were those about 'pointless' work (for example, how your motivation to build Lego models for pay is affected by seeing them being disassembled while you work) and those about how emotions affect short-term decisions which in turn affect long-term behaviour. In the first case I would say there is something quite useful to learn about motivation, even in respect of basic tasks. In the latter it might just make you think twice about decisions you make.
As always, the drawback in this area is how applicable the experimental evidence is in the real world. Though I don't share the view that actually little from behavioural economics experiments holds true elsewhere, we should be alert to the problem. On a similar point, sometimes you do have to query some of the extrapolations made from from fairly specific findings (though I don't share the previous reviewer's scepticism about the research into bonuses - there is a lot more research in this area that points in a similar direction).
Those are minor quibbles though. This is an enjoyable, easy read backed up by interesting research and underpinned by a very personal approach. Given that Ariely's aim is to encourage more human-shaped policy, I'd say his book exemplifies the spirit of his research.