The book describes the two ways in which humans appear to think, System 1 thinking, which is rapid, unconscious and intuitive, and System 2 thinking, which is slower and deliberate. Most of the book is devoted to a comprehensive exploration of System 1 thinking with numerous examples of how it shapes our choices in apparently justifiable ways but which, on closer examination, are less than rational. Our own sense of agency is in large part illusory, a theme taken up by other writers in different contexts. System 2 thinking has its place in the book but one is left wondering how it actually wields its influence, such as it is. We are told it takes effort but beyond that it is not clear.