Mercatante's main argument is that quality was more important than quantity when attempting to explain the course of the Second World War. The German successes in the west in 1940 and in Russia in 1941 and the first part of 1942 came against larger military establishments, at least as well equipped as their German opponents. Even in armour, seen as a key German strength, their opponents matched them - some the French tanks of 1940 were better armed and armoured than most German tanks, and the T-34 famously came as a massive shock to the Germans in 1941. At this stage the larger numbers of Allied tanks were countered by key advantages held by the Germans, including better designed turrets, better optics and better use of communications. Later on the early Panthers were very unreliable and even at their best could never match the serviceability figures of their opponents, while the high fuel consumption and heavy weight of the Tiger limited its usefulness in any mobile warfare. He also looks at the quality of German and Allied military leadership, training and the troops on the ground and argues that as the Allies gained in skill the quality of German leadership declined (greatly helped by Hitler's tendency to sack his more able generals whenever they were forced to withdraw).
His second argument is that the Germans could have won the war if they had focused on seizing Russia's key sources of oil in the Caucasus, thus reducing the Red Army's ability to manoeuvre on the battlefield, as well as doing critical damage to the wider Soviet economy. I'm not quite as convinced by this argument - although it is clear that Germany could have seized the key oilfields if Hitler hadn't become so obsessed with the capture of Stalingrad, I'm not sure how able the weakened German army of 1942 would have been to hold onto this remote area or how quickly its resources could have been exploited.
On occasions Mercatante is rather too dismissive of the value of quantity - the Soviet Union couldn't have survived without the vast numbers of T-34s, heavy tanks and aircraft she produced, and the amazing ability of the Red Army to find fresh troops. Without that quantitative advantage the initial German victories of 1941 would have been enough to win the war in the east.
Overall I agree with the author's main argument. The Germans were being out-produced by their enemies in 1940-41 and still won stunning victories. Later in the war outnumbered German forces were capable of defeating much stronger opponents, at least for short periods of time, while the D-Day landings showed that the western Allies had learnt the lessons of earlier less successful amphibious landings earlier in the war. Sometimes the quantitative side of things is dismissed a little too easily, but his main argument is well made.
1 - The German War Machine on the Eve of War: Myth versus Reality
2 - The Third Reich Ascendant: The Reasons Why
3 - Comparing the World's First Military Superpowers on the Eve of War
4 - History's Bloodiest Conflict Begins
5 - An Inconvenient Decision Confronts Germany's Masters of War
6 -Another Roll of the Dice
7 - Stalingrad in Context
8 - The European War's Periphery
9 - Seizing the Initiative: The Sword versus the Shield
10 - A New Perspective for Explaining D-Day's Outcome
11 - Hitler's Greatest Defeat
12 - How the Third Reich Staved Off Total Defeat during the Summer of 1944
13 - End Game
Author: Steven D. Mercatante