Greg Mankiw understands the economics profession very well. He made his way to the top of the profession and he knows how it is done. Alan Greenspan did follow the path that most economists take to rise within the academy. He became the Chairman of the Fed by following a different path. The Map and The Territory was written to please two audiences: academic economists, and those who might be interested in learning more about the making of public policy. The book will not impress academics because it is not written in their language. It may be of interest to some outside of the academy, but it might have been better if Greenspan had not made an effort please two audiences. Mankiw concludes that the book contains a lot wisdom that has been wrapped in a strange package. Alan Greenspan spent 18 years as the Chairman of the Federal Reserve. The book reflects much of what Greenspan has learned about making public policy. Many will argue that the book was written to defend the policies that he supported. That is probably true, but it provides lessons on the complex problems faced by policy makers at the Fed and the process of getting things done.
I don't usually like the op-eds written by Greg Mankiw because he mixes his knowledge of economics too often with his political philosophy. There is a reason why he was selected as an economics adviser to George Bush and Mitt Romney. However, I think that he did an excellent job of explaining why Alan Greenspan's book might be valuable to some readers and not to others. Wisdom in a strange package is still wisdom.