It's almost impossible to reevaluate the most decisive events of WWII without getting emotionally overexcited in one way or the other. The issues at stake are complex and demand the ability to observe developments from several perspectives simultaneously.
Grayling's book is refreshingly clear and he doesn't resort to the outbursts of rage shown partucularly by people such as German historian Joerg Friedrich. The message is: although the Allied bombing campaigns against the civilian population of Nazi Germany and Imperial Japan were juridically no war crimes and took place in the wider context of a just war against Hitler's bestial tyranny and Japan's cruel expansionism, they were morally inacceptable since they amounted to sheer instruments of terror with little (if any) real military effect.
Grayling especially condemns Bomber Command's nighttime area bombing of German cities in the final stages of the war when, according to Grayling, the outcome of this uniquely brutal global conflict was no longer in doubt. Yet he also makes crystal-clear that he doesn't want to diminish Allied aircrews' massive and brave contribution to overthrowing fascism. The alternative for Bomber Harris' strategy of bombing entire cities to rubble no matter how many civilian lives would be lost would have been to follow the American example of attacking infrastructure serving a highly military purpose (which the USAAF did in day-time raids predominantly). This approach, Grayling argues, would not only have exerted the same strain on Nazi Germany's Luftwaffe to align many of its resources to defending the Reich as the actual campaign did, but it would have also accelerated the downfall of the military-industrial complex providing the Wehrmacht and Goering's Luftwaffe with the means of waging war. Therefore, the war could have been shortened significantly and many lives on all sides could have been saved - and some rather unique architecture as well.
Grayling's book is an interesting and compelling read, his sense of fairness is almost proverbially English and the central thesis of the book certainly deserves closer inspection, especially in light of the current debate on the war on terror (which itself generates terror amongst ordinary people whose involvement in terrorism is at least uncertain). However, he will certainly not convince all the experts, escpecially the military historians, who tend to reduce historic events just to the actual battle action.