From Motherboard TV:

John Coster-Mullen is "a truck-driver with minimal college education, Coster-Mullen taught himself how to build the most detailed replica of an A-bomb ever made. "The secret of the atomic bomb is how easy they are to make."

Last year, Motherboard visited Coster-Mullen to talk with him about his life project: reverse engineering the atomic bombs America dropped on Japan. His findings are available in a book he continuously updates and publishes himself called Atom Bombs: The Top Secret Inside Story of Little Boy and Fat Man, which has received rave reviews from the National Resource Defense Council: "nothing else in the Manhattan Project literature comes close to his exacting breakdown of the bomb's parts."