This is a fine overall chronology of the men, the techniques, the procedures, the multidimensional contributions of science, politics, the military et al that contributed to the atom bomb. Purcell has followed the thread of discovery and research and told of the men -- many of them exiles from their native lands--who participated. The author emphasizes that the pursuit of knowledge for its own sake stands firmly beside the comprehension of the larger goals of producing a new servant of mankind. He has recreated the sense of urgency that drove the lagging American technology to catch up with and pass that of Hitler's Germany before it was too late. Excellent background, understandably written.