I have long thought of developing a World War II literature based curriculum for youth about ages 9 - 13 (roughly 4-8 grade). I have some novels that I think would go well in just such a unit.
First, there is the classic "Number the Stars." This is the type of book that intermediate readers often read. It makes it onto many general reading lists for both social studies tie ins and simple literary selections. It is certainly a great book, but I would go beyond that.
I would want to include "Somebody Named Eva." I think when discussing the Holocaust, it is important to include more. It is necessary to show a complete picture, and kids at this age-level often don't get that. They get a list of goods and bads. Nazis are bad. Germany was bad. Many people went along with bad things. This of course is true, but I would like to see more philosophical discussion on why people go along with bad things. How does it happen? People talk about putting an end to bullying in the classroom, but it will never happen if kids aren't empowered to think about difficult issues and make their own decisions. "Somebody Named Eva" by Joan M. Wolf is the story of the Lebensborn Project, a program designed to make more pure Aryan people. This different angle to the atrocities of the Nazis in Germany during World War II adds dimension to the study.
Then there is the book I just read, "Milkweed" by Jerry Spinelli. This is a great book in its own right! It also gives a lot of history about Warsaw during World War II, particularly the Jewish Ghetto. The book doesn't tackle the Warsaw uprising other than as a passing aside. I think that is a good thing. It keeps it from becoming another cliche. The book is about people. Real people dealing with life, difficulties and moving on. I am surprised I had not heard of the book before.
To add an American side to the unit, I'd select "Lily's Crossing" by Patricia Reilly Giff and "The Green Glass Sea." One tells the story of a girl vacationing at Rockaway Beach and the other is about a girl living with her scientist father in Los Alamo. Both give different views to the things that happened during the war and provide excellent bouncing off points for discussion.