Unfortunately I had to give up part way through reading this as I found the writing slow, ponderous and disorganised. After reading the first few chapters I could not believe there was not one mention of Russia's war against Finland. How could this be left out of any serious discussion of Operation Barbarossa?
There was also little attempt to describe the fighting at the tactical level. The weapons and tactical training of the two different sides made much more difference than the numbers of troops or even the operational planning. Following Stalin's purges the new Russian commanders learned how to fight from the Germans. Yet none of that is discussed in the opening chapters, instead there is just endless discussion of the movement of different numbered divisions which is very hard to follow without a map in front of you.
It's possible that the book gets better as it goes on. I hate to give up on a book part way through but I did not find I was learning anything from this account that I had not already read in general histories of the war. Not a book I would reccomend.