Hanson concludes with a chapter on why the Allies won, and what the results really were. He argues that in the end the Allies were superior in almost every respect. They had more manpower (and womanpower -- even if they mostly were non-combatants, they freed up men for combat roles), better trained in the end. They had far more weapons, mostly of equal or better quality. The Axis powers came up with some surprises, but they were never enough to win. German and Japanese soldiers may have started with an advantage in fighting quality, but attrition wore this down (as it did for Prussia in the Seven Years War) and the Allies developed good troops themselves, often just as good as the Axis (and better than the Italians).
Even those German superguns that proved useful at places like Sevastopol (and also were extremely costly for what good they did) and the paratroops who proved so devastating (at high cost) in 1940-1 didn't enable them to win many of their sieges. Leningrad, Moscow, and Stalingrad never fail (only Leningrad was truly besieged, of course), and neither did Malta.
Germany and Japan were totally defeated, occupied, their cities and industries destroyed, and much of their land taken away (though Japan lost very few Japanese-populated areas). But in the end both recovered well, being the 3rd and 4th largest economies in the world until China pulled ahead decades later. Their economic power wasn't matched by military power, a lesson both were forced to learn after all they had done to others. Italy suffered far more due to occupation (by both sides) during the war, but did at least receive better treatment afterward. They never equaled the others economically, though.
The Allies won, but what they won is another matter. Britain sacrificed virtually its entire empire within 20 years and soon (partly because of their postwar Labor government's socialist policies) saw its economy eclipsed by Germany and Japan. The United States gained little, but it did maintain its world position, and became a lot more engaged in the world in order to prevent World War III. Its wartime propaganda also led to a struggle for equality that would largely be achieved by 1970.
The Soviet Union and China both paid heavy prices for the war, and China an even heavier one afterward as Mao Zedong won a bloody civil war and then terrorized China for decades. The Soviet Union was still ruled by Stalin, but at least after 15 years of an outpouring of blood, the worst was over. It also profiteered nicely out of looted industry, the retention of what they had conquered in connivance with Hitler (and a few extra tidbits, such as Petsamo, the Carpatho-Ukraine, and Tannu Tuva), and a buffer area of enslaved puppet states in eastern and southeastern Europe. Eventually they achieved a brief interval with a modicum of freedom before choosing a new Tsar with KGB experience (Hanson doesn't take things that far himself).
World War II was the Good War, but it still did most of the participants more harm than good. Less harm than letting the Axis win by default, but still harm. But it's always well to remember that this was the fault of the Axis leaders, and to some extent Stalin. Not FDR, Truman, Chamberlain, or Churchill.