Not to contradict your synopsis of the book, but this Amazon reader review drew a different conclusion:

*Whilst D'Este writes a good story, although at times this one moves somewhat slowly, he remains unable to produce a work of great significance. Unfortunately, he allows his dislike of Montgomery to color his work, and an ex-army officer who should know better than that. Whether D'Este likes it or not, there is no Allied Commander with a battle-to-win ratio that touches Mongomery. He was not Manstein, but was a steady hand, and sadly D'Este's selective research, based on a personal bias that appears is his other equally poorly resarched books, fails to take this into account.

This book is a good read, but its conclusions are 'different.' Remembering that no one ever makes good money without finding something new to sell, D'Este's approach is understandable but less than professionally commendable.*