I recommend Victor Davis Hanson’s “The Second World Wars” without hesitation; best single-volume work on the war I’ve ever read. For what it’s worth, he points out that yes, the German army the western allies faced was weaker than it would have been had it not been for the level of fighting in the east. But the distance between Normandy and the Elbe is about three quarters of the distance between Moscow and Berlin and the Allies covered that distance in eleven months, rather than the four years the Red Army took…and at five percent of the casualties.