Candide
Any French edition or English translation.
Voltaire was a true man of action, a knight of the Holy Ghost. He plunged fiercely into the human arena, and fought through a laborious life, against obscurantism, stupidity and tyranny. He had a clear-cut, aristocratic mind. He hated mystical balderdash, clumsy barbarity, and stupid hypocrisy.
Candide is not only a complete refutation of optimism; it is a book full of that mischievous humor, which has the power, more than anything else, of reconciling us to the business of enduring life.