Memoirs of Pylcyn, a penal battalion commander. His life could be used to make a great war movie. Also, explains in details how did penal battalions work in the Red Army.
Alexander Pylcyn memoirs on Amazon
Very interesting and rare - from penal company commander.
Cannot vouch for translation quality - I've read it in russian and it was lively, no-nonsense and coherent reading.
I really recommend picking up this book https://www.amazon.com/Penalty-Strike-Commander-Stackpole-Military/dp/0811735990
Read it in full and finally stop repeating these myths