Excellent book. As far as I know, the author is still alive. I believe the experiences described in the book are accurate but given the vengeance being exacted by the Russians at the time of writing, obfuscation of anything that could connect the story teller, or his surviving friends to acts considered crimes by the Russians was necessary.
My take on “Forgotten Soldier” is that I don’t doubt that those things happened, or at least that’s what soldiers remember happening. But they may not all have been the experience of one guy. In other words, it’s a synthesis of some common experiences. And I consider it an accurate portrayal of life on the Eastern Front.