Beautiful story of German women during World War II

The story is divided in two periods and two places: the United States in the 1990s and Germany (Weimar) during the war. Two eras, two women, a mother who becomes the mistress of a Nazi and daughter, history professor at an American University, who goes in search of his past. No value judgment, no moralizing look or complacent about the history of one by the other, just a girl who wants to know his origins and understand where it comes from. Very beautiful novel to discover.