'Henry & June'
Based on the book of the same name by Anaïs Nin, this movie chronicles Nin's time in Paris with Henry Miller and his wife June. There's a lot going on here: threesomes, sexual explorations, and, more than anything, the sexual awakening of Nin that would forever change her and her thoughts about monogamy. It was also the first movie in the U.S. that got an NC-17 rating.