Those familiar with WWII would know that the Normandy landings were one of its milestones but most would not know the espionage operations that went towards ensuring its success, and their extent. 'Double Cross' does an excellent job of introducing the reader to Operation Fortitude - the operation to deceive the Germans about the landing spots, and to keep them away even after the landings.
6 double agents form the core of the narrative, and while the build-up was slightly slow since each has to be introduced in turn, the pace picks up in the middle. Despite having to cover 6 characters, the author did a good job of distinguishing them from each other, and more importantly, making me feel for them, warts and all. And even though the success of the Normandy landings was a foregone conclusion, the final chapters were still enthralling, especially after one realises how much the agents had risked and sacrificed in order to achieve what they did.
An excellent book overall and I will be looking forward to reading more of the author's other works.