Nicomachean Ethics

For one swallow does not make a summer, nor does one day; and so too one day, or a short time, does not make a man blessed and happy.

Widely considered to be one of the most important works written on philosophy, Aristotle's Nicomachean Ethics is separated into 10 books that cover topics such as friendship, happiness, and the invaluable virtues that a person should strive to obtain.