The Prince by Niccolò Machiavelli
Machiavelli was born in 1469 in Florence, Italy. His father was a poor lawyer and his mother was a poet. Being a natural politician, he entered into government service. He often accompanied diplomats to neighboring countries, but being of "low" birth he was only an assistant. But his shrewd observations were noticed.
Machiavelli lived in a very volatile era. Italy was divided into city-states. France, Spain and the Holy Roman Empire were continuously invading these territories. The Medici family had controlled Florence for a century, but in 1494 Charles VIII dove them out. Florence becomes a republic until 1512 when the Medici family regain power. Machiavelli is ousted from government and exiled to his country farm. Here he begins writing.
The Prince was his attempt to regain favor with the Medici's and return to government service. In The Prince he attempts to council a new ruler on the methods he should use to keep his kingdom secure. He writes advice on the military, the public, nobility, foreign relations, etc. He picks through battle after battle and explains what went wrong and what should have been done.
The Prince is the book which gave rise to the current Machiavellian definition-cunning and deceptive. He writes "...one looks at the outcome." This has been take to mean "the end justifies the means." But what Machiavelli is saying is that people don't care what a prince does as long as it benefits them. This is true enough.