All of Us by Katrina Nannestad

When twelve-year-old Viggo and his friends Finn, Tove, Birgitte and Konrad start writing rude letters to Hitler, it's just a game. But soon, they find themselves writing an underground newspaper, their words inspiring people all over Copenhagen to commit small acts of defiance.

Then news leaks of the Nazis' plans to round up all of Denmark's Jews in a single night. It's time for one huge act of defiance. Can Viggo and his friends work together to save Tove? Can an entire population work together to save their Jews?