Sun Tzu's The Art of War (Oxford University Press, 1963; 197 (Originally written in 500 BCE and translated by Samuel B. Griffiths)) is one book that has inspired several other books. It's been applied to various fields from business to friendship and more. In this book, Sun Tzu discusses what a good General should do if he is to win wars. The discusses almost everything that one needs to do and know about war and its effects from war-induced inflation to food shortages that accompanies it.
According to Sun Tzu
 War is a matter of vital importance to the State; the province of life or death; the road to survival or ruin. It is mandatory that it be thorougly studied. 
Regardless of this, Sun Tzu puts premium taking enemies and their state whole with as minimum a damage as possible. He writes
 Generally in war the best policy is to take a state intact; to ruin it is inferior to this. [Page 77]
He goes on further to explain
 For to win one hundred victories in one hundred battles is not the acme of skill. To subdue the enemy without fighting is the acme of skill. [Page 77]
This advise runs through the entire text. After reading this book I get to understand the importance and premium of mind-games. For instance, how does one overcome the enemy without fighting? He explains the importance of mind games. Mind games are important to make the enemy feel weak (even when he is strong) and also to boost the morale of the people back home for it is in their acceptance and the harmony that springs forth that wars are won. Here, today, ones ability to manipulate the media counts very much. Sun Tzu says attack the enemy's strategy. Again he says "all warfare is based on deception" and the General must do everything possible not to give out much information to the enemy. Deception puts the enemy in an unstable state:
 When near, make it appear that you are far away; when far away, that you are near.[Page 66]
 Offer the enemy a bait to lure him; feign disorder and strike him. [Page 66]
 When he concentrates, prepare against him; where he is strong, avoid him. [page 67]
 Pretend inferiority and encourage his arrogance. [Page 67]
Whilst keeping the enemy in the dark or in false knowledge, the General must work to be know the enemy's strategy; and here Sun Tzu recommends the use of spies (native, doubled, inside, expendable and and living). He showed how best to employ and deploy all these spies effectively to the advantage of the skilled General. All these is a preparation towards subduing the enemy without fighting or causing unnecessary deaths. Has anything change since 500 BCE when Sun Tzu wrote this book? It explains why defections were high during the Cold War and might explain why space technology and exploration is on the increase.
The advise that stood out, under Offensive Strategy, (and which has been given by several sages of the past) with applications in almost every field of human edeavour were:
 'Know the enemy and know yourself; in a hundred battles you will never be in peril.[Page 84]
 When you are ignorant of the enemy but know yourself, your chances of winning or losing are equal. [Page 84]
 If ignorant of the enemy and of yourself, you are certain in every battle to be in peril. [Page 84]
The importance of knowing oneself and knowing the external conditions - the enemy, the strategy, the terrain etc - was emphatically stated. Finally, even before the UN Convention Against Torture came into force in 1987, Sun Tzu in 500 BCE has written that
 Treat captives well, and care for them. 
The information provided in the book were written in short numbered paragraphs like aphorisms, sometimes requiring explanation from the translator, at other times commentaries from equally excellent Generals who have used Sun Tzu's guidelines like Tsa'o Tsa'o, for the reader to understand. This is a quick read but it will help much if it is read slowly so that the contents could be well internalised. As earlier stated, its application is beyond the subject of war.
If you have not read it, kindly do.