[Rizla]

Willi Heinrich's The Willing Flesh renamed The Cross of Iron after the film based on it. Also The Crack of Doom by the same author. Heinrich was in the German retreat from Russia.

The Forgotten Soldier by Guy Sajer.

The Last Enemy by Richard Hillary. I believe this is available on Gutenberg.

One of our Bombers is Missing (originally published as Never so Young). Brennan was an American who volunteered for the RAF prior to American entry into the war, and was ruined by it.

All of it written by people who took part in WWII on both sides. Nothing by a Russian, though. Stalin probably killed them all or burned their books.