In Emil and Karl, so many horrible things are happening in the text.
Karl's mother is taken away from him by the Nazi regime and his father died long before because he fought for rights; he was a Socialist.

Emil's mother is also taken away because she is very ill. His father was killed by the Nazi regime and sent to Emil and his mother, cremated.

It's easy to see there is no justice in Emil and Karl. It's like a little kid version of showing racism and the Holocaust. It's not really for little kids though, you wouldn't read this to elementary school kids.
It's especially amazing that this book was written DURING the Holocaust, not after.

Also, I think that in this text, Emil and Karl's point of views are missing. Karl just doesn't understand WHY Hitler wants to get rid of Jews and others if they're not Aryan. I'm not sure he and Emil actually understand WHY though. It's just that they're parents told they Hitler was bad. Emil is sort of like the person who doesn't know what to do. He might WANT to be different because he's hated so much. He might think "Why did I have to be like this? Why couldn't I be RIGHT and not HORRIBLE as they say I am?"

This book is very serious and that it needs to be read with an open mind.