Can't leave it at one book, because there are four which all tie into a whole: 1. The Book of Five Rings (how to manage yourself) 2. The Art of War (how to ma

Can't leave it at one book, because there are four which all tie into a whole: 1. The Book of Five Rings (how to manage yourself) 2. The Art of War (how to manage your campaign) 3. The Prince (how to manage your domain) 4. Proverbs (the wisdom of generations of people in positions of power)