In the past couple months? Tough, but I'd have to say
The Warsaw Anagrams by Richard Zimler about an elderly Jew in the Warsaw Ghetto who tries to solve the murder of his young nephew. Grim and felt a little disjointed at times, and yet it's stayed with me. Always a sign of a good one. I reviewed it
here, by the way.
There are others. My secondary book is the German version of
Every Man Dies Alone by Hans Fallada, based on the true story of a modest Berlin couple who decide to resist the Nazis after losing their son in the war (
Jeder Stirbt für Sich Allein, or
Alone in Berlin [UK]). Really enjoying it when I can get to it.
But there's so many!