Thought by many to be Machiavelli's true philosophy on politics and government, the Discourses are a must read. This work actually predates The Prince and is a political history of his times.
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Also highly recommended by Corsair's:
The Ultimate Hitchhiker's Guide to the Galaxy
Douglas Adams 'Trilogy' (there are five books) is one of the greatest. More humor than true sci-fi, it is a tale of the human experience. It also does much to examine society and our often convoluted logic. This book will not make you a great analyst. It will make you laugh and it is liable to open your mind. There really isn't much better than that.
Money Mischief : Episodes in Monetary History
This book is among Friedman's most approachable offerings. It is a series of case studies into monetary policy in the 20th century. It showcases Friedman's theories and highlights the thinking of the Chicago School.