These two books are very short and go together very well.
A new edition of the highly exalted and infamous discourse containing observations and instructions on the significance of a rise to power. For nearly half a millennium, its logical and direct analysis of diplomacy, war-craft, and human nature has commanded a wise ruler in all who read it. No collection of political philosophy and history is complete without it.
The Art of War:
This standard work about the strategy of warfare was written by the Chinese general Sun Tzu (aka Sunzi and Sun Wu) in around 500 BC. It is believed to be the oldest military treatise in the world. The principles taught in this book can also be used in other situations than warfare; this book gives tips on how to outsmart others. This book is an interesting read and will certainly give you a few tips on how to be a better strategist. If you are interested in 'Art of War' by Sun Tzu than I would recommend trying to get this version of it. At the bottom of this review I will copy a few sentences from the first chapter of this book as a sample. I do recommend this book to everybody, and not just to people who are interested in military strategy.