Saboteurs: The Nazi Raid on America, by Michael Dobbs

In the past few years, several books have been written about an event I'd only heard of in the fantastic BBC documentary series Secrets of World War II. Suddenly, there are plenty of books detailing "Operation Pastorius," a unique one in that German agents were sent to the United States in 1942 to perform sabotage operations and spy on the American war effort.