Side story to the Tattooist of Auschwitz

I have not yet read The Tattooist of Auschwitz, it's not my typical genre. But after reading this I may have to. I haven't read this side of the story. The Allies were, of course, hard on the Germans when they lost. But I never thought about those wrongfully condemned. Those made to do horrible things to survive, only to be freed and imprisoned again.