The cover is misleading. The book does not refer to any kind of alternate universe. It is a collection of essays written by different scholars. The authors ponder various possible scenarios that could have played out during the Second World War. They examine what could have gone differently in the course of WWII if another step had been taken at one point or another by one actor or another. The proposed scenarios rely on the available information about the manpower, resources, and military and economic potentials of the countries involved in WWII. They try not to diverge from the developments familiar from the general history of the period and avoid suggesting things that were not feasible given the circumstances.
Just to give one example, the authors posit that Germany would probably have not been able to achieve a victory over the USSR due to the relative strength of the Soviet and German potential for mobilization. The Soviets had greater capabilities to mobilize forces and form reserve armies than the Germans. The only chance for Nazi Germany was to try to appeal to Soviet populations and gain their support. There were many disconcerted people who had suffered from Stalin's repressive rule. As the authors note, the conceivability of such a course of events cannot be ruled out if the Reich had been able to change its ruthless tactics of turning local people into slaves. Given Hitler's views, such a paradigm shift would hardly have been possible.
Most chapters end up stating that making different decisions would not probably have had a decisive effect on the course of events. The final results would probably have been pretty much the same. The last chapter What if Hitler had won the war? which explores when, how, and if Hitler might have won also tends to testify to this conclusion.
It seems that if we look at the bigger picture, the Allied Forces were likely to prevail over the Axis powers in most scenarios. However, the way the war was unfolding, the number of victims, both among military and civilians, and the time and course of major operations could have changed significantly had the main actors opted for decisions other than those they happened to take in real life.
The book encompasses a variety of different scenarios across all the theatres of the Second World War, from Europe to the Pacific front. Most alternatives discussed in this volume remain mainly in the realm of speculation. The authors look to answer such specific questions as What if the French had launched an all-out attack to help the Poles?, What if Hitler had been able to negotiate peace with Britain in June-July 1940? What if the German 1942 summer offensive had been focused on Moscow? What if Hitler had been killed on 20 July 1944? What if communication intelligence had not been available during the Pacific War? What if Britain had rearmed earlier in the 1930s or had adopted a wartime naval strategy consistent with her fleet strength? What if the Germans had not invaded Scandinavia?, to name a few.
Almost all subtitles concern the "what if" question.
The volume discusses the role of Ultra, the famous cypher machine, and its Pacific counterpart called Magic. They seem to have helped the Allies a lot in achieving their goals.
One of the conclusions one can draw from this non-fiction book is the importance of timing. The result of so many decisions often depends on whether they are implemented at the right moment.
Although accidents may play an important part, they often do not lead to key changes. However, those differences matter from a humanistic point of view. Every action that may save people's lives deserves great attention, even if it does not cause a major shift in the course of events.
Overall, this book does not seem to be very accessible. At times I found myself trudging through the account. I would recommend it to those who are both versed in the history of WWII and interested in the decision-making process.
The book also offers a few lessons about the period of WWII as the course of affairs from real history is often addressed. However, alternatives can at certain points be confused with the historical sequence of events.
P.S. The Soviets are several times called the Russians in the book. I know that this has been quite common in non-fiction books and in general discourse, but today it may send the wrong message. Different nationalities fought in the Soviet army. Worse, referring to all of them as 'Russians' means in a certain way supporting narratives used and abused by the Kremlin in its current propaganda.