Prisoner of Night and Fog by Anne Blankman

In 1930s Munich, danger lurks behind dark corners, and secrets are buried deep within the city. But Gretchen Müller, who grew up in the National Socialist Party under the wing of her "uncle" Dolf, has been shielded from that side of society ever since her father traded his life for Dolf's, and Gretchen is his favorite. This harrowing and evocative story about an ordinary girl faced with the extraordinary decision to give up everything she's ever believed and to trust her own heart instead.