Les Liaisons dangereuses by Pierre Choderlos de Laclos
The complex moral ambiguities of seduction and revenge make this one of the most scandalous and controversial novels in European literature. Its prime movers, the Vicomte de Valmont and the Marquise de Merteuil - gifted, wealthy, and bored - form an unholy alliance and turn seduction into a game. And they play this game with such wit and style that it is impossible not to admire them, until they discover mysterious rules that they cannot understand. In the ensuing battle there can be no winners, and the innocent suffer with the guilty.