First, D'Este actually spoke with numerous people who are mentioned in the text, and was able to include personal observations or comments by several of the commanders who were still living, either because they were made to him or because he is in many cases reciting the history of the … history of D-Day. By that I mean that he spends much time, especially at the end of the book, reciting how the official histories of the armies were written in the United States and in Great Britain, and in many places that required reference to letters from Eisenhower or Montgomery or others who were commenting on accounts that were being or already had been written.
Why? Because given the time period that the book was being written, the two sides were still arguing over who was right and who was wrong in the conduct of the campaign. No, no, not the Allies and the Germans – the Americans and the British. At the time D'Este was writing, the campaign in Normandy was still a subject of serious controversy between, basically proponents and detractors of Field Marshal Montgomery, with the sides breaking down largely on national lines. According to D'Este, the U.S. Army's account of the war was largely balanced and correct, but the British account was, for political reasons, decidedly not, and gave Montgomery far more credit than was appropriate. At bottom this was because of Monty's decision both during and after the campaign to pretend that everything had gone according to his plan, and absolutely so at his end of the front. Pay no attention to the Germans holding Caen for six weeks longer than predicted, in other words. As a result, D'Este spends an inordinate amount of time documenting what Montogomery had said he would do, and what he did, seeking to disprove this claim. He does not present this as a negative on Montgomery's generalship – had he admitted that he had had to changes his plans to deal effectively with changed circumstances on the ground it would have been to his credit that he did so as effectively as he did. But he steadfastly denied that was the case, and the British accounts generally backed him up.
Decision in Normandy is one of the older of the World War II books I have read lately, and it shows. Closer to the time of the events it recounts, it shows the grudges that the Allied military leaders brought back at the end of the war, and how they affected the history that was being written – so much so that almost 40 years after the events D'Este finds it appropriate to document the history of the documentation of the history of the campaign. But it also means that he is frequently noting that certain sources are not yet available, or have just become available, which makes the thought of being able to read texts that have the benefit of over three decades of additional sources exciting. (That I am sitting at home on a Friday night writing that this is exciting is perhaps best not examined too closely). I don't note the age as a bad thing – it just means that things are emphasized a little differently than they would if the author was dealing with the controversies over McClellan's conduct as head of the Union Army.
But for these reasons, while the book is a good one about the campaign (I wonder how it would compare to John Keegan's Six Armies in Normandy published the year before – but I'm not willing to reread that one just yet) it is equally interesting for the stories it tells about the postwar grousing by the participants about each others' version of events, and the perspective it gives on historical scholarship when the participants were still alive, kicking, and nursing grudges.