The Kommandant's Girl by Pam Jenoff

Not a bad story, based in part on actual events. Polish Emma Bau is recently married to Jacob when Germany invades her country. Jacob is active in the resistance, leaving Emma to live with her parents. Finding her parents evicted from their home and placed in a Jewish ghetto, Emma has a hard time facing the truth of what is happening. When she is smuggled out and sent to live with Jocob's Catholic cousin, she pretends to be a gentile and is caught up in the intrigue of the fight of the resistance. Sandy Penton