More than a half-century later, Gönner’s grandson, the New Yorker staff writer Burkhard Bilger, began a years-long quest to come to terms with what his grandfather had done. That reckoning — which included meeting surviving townspeople, jogging relatives’ memories, and excavating hidden archives — evolved into his newest book, “ Fatherland: A Memoir of War, Conscience, and Family Secrets .” For four years, Karl Gönner ruled over French civilians as a Nazi party chief, guiding local children through German “re-education” programs. Allied authorities finally called him to account for his wartime deeds in 1946. “You established yourself as Ortsgruppenleiter in...