Ben MacIntyre has written a series of books dealing with the Allies adventures in misleading the Nazis during World War II. Agent Zigzag and Operation Mincemeat were his 2 previous books on this subject. Double Cross deals with the Normandy invasion, or more specifically with "Operation Fortitude." The operation was an elaborate ruse to keep Germany's attention focused on Calais, while the real invasion site was to be the beaches of Normandy.
British military intelligence seems to be particularly adept at putting together the most surreal series of events and having the Nazis fall for it every time. The group involved in this charade were actually double agents. Several were actively recruited by the British, but others simply walked up to the British Embassy and volunteered. One actually started sending his own false information to the Germans after having his offers to spy be dismissed because he was considered a 'crackpot." The group is almost unbelievable: bored German rich boys, a double dealing import/export business owner, the organizer of a French spy network who is actually Polish, a bored rich Peruvian, a poultry farmer and a woman who actually wanted to spy for Germany and almost brought down the whole network over her beloved dog. These people were so entrenched in the German intelligence service one of them was actively involved in a plot to murder Hitler.
This book would seem to be fiction, except the background comes from recently released military documents. MacIntyre makes full use of them as he uses recorded conversations, payment histories and diaries to bring the charade to life.
I love MacIntyre's books. You simply can't make these stories up - they are almost bizarre in the way they unfold. But history supports them! These books read like a spy story, which of course they are, but they have the added bonus of being true. I recommend all his books.