
A clear, well-researched, and very readable account of Operation Overlord as told by survivors. Skip the Ambrose book and read this instead.
A small nit: The assertion that secrecy, i.e. absence of information was the key espionage tactic at play here is not quite right. Instead, the allies put a massive amount of effort into misinformation.
Going from memory… In his book, The Longest Day, Cornelius Ryan reported that the Germans knew the location, the approximate dates, and had even determined what signal would be sent to the French Resistance (a particular stanza in a poem read in a radio broadcast.) Getting higher ups in the German apparatus to believe that they had figured it all out was the main failure.
A lot of the German high command was convinced that the landings would be at the Pas de Calais (the shortest crossing). The Allies did a lot to support this view, including using Gen Patton as the commander of the fake army that would conduct this crossing. Even after the Normandy landings, the Germans were very reluctant to commit the forces that were ready for the 'fake' invasion (which of course never happened).
"In the hands of a writer with a flair for the dramatic and the ability to turn a phrase such as Cornelius Ryan [Wrote The Longest Day and A Bridge Too Far] [...], W.E.B. Griffin, Tom Clancy, or Donald Burgett [Wrote "first-hand accounts" and is one of the subjects of Band of Brothers], this book would have been a compelling read. However, Stephen Harding managed to turn [this] into a dull trudge of boredom."
They seem to have difficulty distinguishing fiction (and popular non-fiction) from history, to be complaining that this is in fact a history book.