Ariely presents fifteen different ways where humans believe they are acting rationally - but in actuality, environmental factors and other secondary circumstances impact us so much that we behave counter to how logic would predict we should act. Essentially he tells us when we are predictably irrationally, as the title implies.
I liked this book a lot. Some of it was new, some of it I had already heard and read about (such as the trust in companies, the bit of price and pills like Tylenol correlation with placebo effects, and a couple other). Some things were new, such as the comparative effective in the first chapter or the ideas about social and monetary networks.
I didn't always agree with his conclusions or his reflections upon finishing reading about his experiments, but they were always something to consider. I, for one, still wouldn't pay for everyone's dinner or lunch at a time haha. I didn't really like his chapters on the Zero. The experiments and discussion were interesting, but when it got to the reflections, I just didn't agree. There also were a couple moments where I thought about the irrationality of the subject, and felt as if I could make a few counterarguments to the rationality of the switch in behavior.
Also, I think he has a bit of an optimistic viewpoint on changing the world through understanding how humanity is predictably irrational - especially in light of healthcare and education.
Overall, I quite enjoyed reading this book because many of the things he said did apply to my own life that I had not realized beforehand.
Four stars because I did like the book a lot and it made me think quite a bit. Not hard to read, either.
Recommended for those who are interested in a bit of psychology and understanding your own decision making. Recommended for everyone, really.