I recommend this powerful historical novel. The scene is Germany in 1938. Hitler is the leader and hugely popular - all the boys seem to be in Hitler Youth and most people seem eager to denounce Jews and anyone disloyal to the Nazi regime.
Ann Lindsay is a 14-year-old English orphan whose Uncle Dick, a journalist and her guardian, has brought her along as he tours Germany and writes about it for a newspaper. Ann has learned to understand German well. She wakes up in bed in a strange house with a kind German woman caring for her and learns that she and Uncle Dick were both badly hurt in a car accident. He's in the hospital, but she "only" had a concussion and was fine recovering in a home with good care.
I don't think it's too much of a spoiler to say that as Ann recovers she encounters two Jewish girls who are in hiding. At that time, the government was happy for Jews to "self-deport", but these particular girls are in danger, since the Gestapo would like to use them to get at a wanted person. Ann also befriends a bitter, lonely rich girl, and struggles to hide the secret of her new Jewish friends from this loyal young Nazi.
Another important character is her hostess' young son, who doesn't believe the Nazi ideology but enjoys and is influenced by the Hitler Youth he's required to belong to. When Krystalnacht happens, he is torn between normal boyish delight in the bombs his comrades are setting off and concern for the Jewish shopkeepers whose property is being destroyed.
The Catholic church plays a noble part, in the persons of some indomitable nuns.
This YA book has a lot of suspense and some violence so would probably not be ideal for sensitive children under 10 or so, but there are no other content considerations. It ends pretty well. It's certainly interesting and deep enough for an adult. The situation in Germany at that time is a cautionary tale I wish more Americans would pay heed to.
We've had this book for decades but I couldn't remember if I'd read it before. It took me till more than halfway through to realize that I had - there was one memorable (and ironic) conversation which continues to be the only thing I remember from my previous reading.