As in many of his books,John McPhee and his capacious memory and notebook spend time with interesting people--in this case a man who begins his career designing nuclear weapons at the start of the cold war. Also like others of his books, our intest is captured as much by the personalities as the subject. Besides meeting a fascinating and hightly idiosyncractic physicist, I learned enough nuclear physics from this little book to really liven up my 9th grade physics classes. I gave 4 stars because the book is necessarily dated, but I'm awfully glad we are a step or two further from the brink than some experts at the time expected, since we did not go down the road to using plutonium in nuclear reactors. On the other hand, the threat of terrorism is greater than it seemed then.