Like Niccolo Machiavelli's The Prince, Sun Tzu's The Art of War is an ancient book that has been co-opted by today's powerful or ambitious to gain insights into martial, political, business or other strategising.
The Prince is a treatise about achieving and maintaining power and its best known line is: "it is best to be both feared and loved; however, if one cannot be both it is better to be feared than loved". Napoleon and Mussolini were among those influenced and the effect of Machiavelli's work - written in 1513 - was such that his name has become an adjective denoting slyness, deception or, to sympathetic eyes, realism.
It is not known whether Sun Tzu actually existed but The Art of War - which perhaps dates back to 400 BC although nobody is too sure - suggests that he made his name as a general when tested by the king, who asked him to train a harem of hundreds of concubines. Sun Tzu divided the group in two, each led by a favoured concubine of the king. When the concubines giggled at his instructions, he had their leaders executed and when the king complained he argued that the duty of a general is to follow his first set of instructions and the duty of those being instructed was to follow orders.
This hard-line literalism isn't entirely typical of the work as a whole, however. Although it has a lot to say about the importance of tricking the enemy ("All warfare is based on deception"), luring strategic errors from enemies, ruthlessly exploiting vulnerabilities, being suspicious of motives and acting with speed, it also recommends that leaders be serene and inscrutable, and praises diplomacy ("Seizing the enemy without fighting is the most skilful way"), self-knowledge and due diligence ("So it is said that if you know your enemies and know yourself, you will fight without danger in battles"), timing and paying due attention to prevailing conditions such as the weather.
However, perhaps the main reason that The Art of War has proven so popular is that it is written in an aphoristic style, full of maxims and easily digestible one-liners. In this sense, it is father to the groaning shelves of business books stuffed with homely gobbets of wisdom. It is also widely seen as a way to understand Chinese culture and commerce.
Napoleon read it, as did Vietkong leaders and US generals MacArthur and Schwarzkopf. However, today it is best known as the handbook of choice for business managers such as Salesforce.com CEO Marc Benioff and sport coaches like Chelsea's Luiz Felipe Scolari. Even if you're suspicious of faddish affections for foreign cultural wisdom, The Art of War is worth exploring and can be picked up for pennies on Amazon.