VOLK is Piers Anthonys serious novel of World War II and forbidden love, featuring a romance between a Nazi SS officer and his American friends fianc, a pacifist Quaker lady. Politically incorrect, it covers some hard truths. Not all Nazis were evil, and the Allies also kept death camps.
The author was in Europe as a child, deported in 1940 and was raised a Quaker, so has some basis to address the subjects.