Goes without saying that
Prof John Eriksson's books Road to Berlin and Road to Stalingrad are excellent.
Tony le Tissier's Battle of Berlin is very good also.
Horrido! by Rudel is quite good although he loves himself way too much.
"Samurai" by Saburo Sakai [Jap ace] is brilliant... bit like a diary with his thoughts interlinked in
Beavor's books are also good but a little overused and overquoted these days