The book is in two parts. The first 'Unconscious intelligence' looks at where our intuition comes from - the nature and evolution of our brains, and how we have learned to make quick decisions. The second part 'Gut feelings in action' gives some real world examples of the benefits of using our intution. When people are asked a question, such as which of two cities is larger, those with limited knowledge who only recognise one of them often do better than the more knowledgeable ones. Gigerenzer goes on to describe how making decisions based on a single criterion is likely to be better than a detailed weighing of all of the information available. There is also chapter on how this sort of decision making can provide benefits in healthcare. The book ends with chapters on moral values and social instincts.
The subject of intuition and it benefits is a popular one for authors - or at least I've read quite a few books on this topic recently. I think that Gut Feelings is one of the best in that it is amusing and easy to read, but is also useful as a guide for those wishing to improve their decision making.