Heisenberg's War: The Secret History of the German Bomb

One of the most important--and controversial--aspects of the history of the Second World War is the failure of the Germans to build an atomic bomb.  Germany was the birthplace of modern physics; it possessed the raw materials and the industrial base, and although many leading scientists fled from Hitler, it still commanded key intellectual resources.  Yet at the end of the war the Germans had no bomb, and their nuclear research program was found to be negligible.  What happened?