Had to look this one up because the title is a bit misleading—it's not literally about bomb-making for Hitler. The book is called 'Making Bombs for Hitler' and follows a Ukrainian girl, Lida, during WWII. After being captured by Nazis, she's sent to a forced labor camp where she and other children are made to work in a factory.
Lida's the main character, and the story is really about her and her younger sister, Larissa, who gets separated from her. There's also another girl in the camp, Luka, who becomes a close friend. It's told entirely from Lida's perspective, so you're deep in her survival and her constant fear for Larissa.
It's a brutal, heartbreaking read focused on those kids trying to stay human. The adults are mostly guards or distant figures of authority, so the character list stays tight on the prisoners.