It is hard to decide the greatest books in the human history, however, it is sometimes said that there are three masterpieces that no other known related work can compare. They are "The Prince", "The Art of War", and "The Art of Worldly Wisdom".
The prince, originally called (Il Principe), was written by Niccolò Machiavelli in 1513. "The theories expressed in The Prince describe methods that an aspiring prince can use to acquire the throne, or an existing prince can use to maintain his reign." (Wikipedia).
The art of war, originally in ancient Chinese (孙子兵法), was Sun Tzu's work during 6th century BC, which "has long been praised as the definitive work on military strategies and tactics of its time." (Wikipedia).
The art of worldly wisdom, written in Spanish by Balthasar Gracian in 1637 (Oraculo manual y arte de prudencia), gives advices on our personal lives. While The Art of War and The Prince are generally concerned with affairs of the state, The Art of Worldly Wisdom ranks among the most notable and popular works of philosophical advice.