18th Century French epistolary novel about 2 sociopaths who go around seducing and manipulating people for either revenge (usually on 3rd parties) or their own amusement, destroying the lives of others and eventually themselves. 
 The Marquise de Merteuil wants to revenge herself on a former lover--so she seduces his convent-bred fiancee (her own cousin, Cecile Volanges), then attempts to arrange her to be seduced by her music teacher (a man who truly loves her) and/or the Marquise's partner in crime and former lover, Valmont. But Valmont is involved in a project of his own--seducing the Presidente de Tourvel, a religious woman and faithful wife who presents a challenge to his skills, so he is at first reluctant. When he finds out Cecile's mother has warned the Presidente about him, he debauches Cecile in revenge (he initially more or less rapes her; he teaches her only a crude sexual vocabulary; he asks of her things he says he would not ask of whores; he impregnates her; etc.) and she just takes it. Although he is a douchebag through and through, he has a certain wit that left me laughing at times; Cecile on the other hand just seemed really dim, but after re-reading I realized she's only 15! She's a kid and way out of her depth. 
 While de Merteuil and Valmont's stratagems are originally successful, the two of them end up at odds in their own relationship and eventually bring down the kind of disaster that leaves all but one of the main characters dead, in a convent, or both (except for the Marquise, whose fate is worse, if you can imagine). It's a fascinating book populated with really interesting psychopathology and relationships, and it's a tribute to its power to spark the imagination that I can think, offhand, of 3 very different movie treatments of it (2 of which I've seen). However, there is no one to really like in this book. Valmont and Merteuil have a few redeeming characteristics, but their typical callousness towards others makes them villains (in fact, reading this, I thought if the French aristocracy really did behave like this than NO WONDER the Revolution happened); Cecile, her mother, and her would-be-lover are dupes; the Presidente de Tourvel seems overemotional but remains enough of a cipher and victim and just not very *interesting* compared to the other characters. 
 I really loved this book. Read it multiple times, psychoanalyzing the characters.