[I]t's also a great general guide on how to understand complex situations and avoid our natural cognitive biases in reasoning.
I've not read it all, but it aims not only to give the reader an understanding of the limitations of our reasoning, but also how to overcome them when trying to think about tricky problems.
A central focus of this book is to illuminate the role of the observer in determining what is observed and how it is interpreted. People construct their own version of "reality" on the basis of information provided by the senses, but this sensory input is mediated by complex mental processes that determine which information is attended to, how it is organized, and the meaning attributed to it. What people perceive, how readily they perceive it, and how they process this information after receiving it are all strongly influenced by past experience, education, cultural values, role requirements, and organizational norms, as well as by the specifics of the information received.
There is the key to understanding why people make different decisions based on the same data, in fact why they may not perceive the data as the same in the first place. It's not news to me that my reality differs considerably from that of many of the people I associate with, including friends and family; I literally perceive the world differently from the way they do, using different tools to gather data as well as analyze it. If you follow the links you can download a pdf of this text, which will be worth my time at least.