I originally read Heinrich von Kleist's "Die Marquise von O..." in a German class. Renting the movie, I naturally had to wonder whether or not they would stay faithful to the novel. They did. This story of an 18th century marquise (Edith Clever) who inexplicably becomes pregnant has surprises at every corner. In case you don't know the whole story, I won't spoil it for you, but you will be surprised at what happens. Strong performances by Clever and Bruno Ganz as The Count carry the movie, as does the perfect direction from Eric Rohmer.
Oh, and in case you're wondering about that "O...", it's deliberately incomplete, as are some other names in the story.