For those who can stand it, I recommend the film
Come and See, a no-holds-barred depiction of the gruesome reality of the Eastern Front, from the Russian perspective. It's available from free viewing on YouTube, with English subtitles. Warning, this film is not for the young or the the squeamish:
Come and See
For those who cannot stand watching that film, I recommend this book which tells the true story of a young Ukrainian boy who is drawn into the maelstrom of the war between the totalitarians and their allies:
Hell's Mouth: Confessions of Count Nepomuk