Last night I finished Cassidy's biography on Heisenberg, and so wanted to write a brief review.
The author is a scientist-turned-historian writing a biography on a great scientist. As such, the book is really writing three stories that all occur simultaneously. The obvious one is the life that Heisenberg led. You also get a brief synopsis of his scientific achievements as they were developed and published. To put both of these stories in context, however, the third story being told is a pseudo-personal history of Germany. To give the reader a better understanding of this history, Cassidy will give brief anecdotes about the figures that appear in Heisenberg's life that Heisenberg would not have known, such as the activities of Oppenheimer during the second world war, or the actions of influential Nazi party individuals that, entirely unknown to Heisenberg, essentially saved his life.
There is a historical controversy about Heisenberg dealing with his actions during World War II. The author takes great pains to tread around this with tact, and succeeds at doing so while giving information around the controversial events. He lays out why certain pieces of evidence are suspect, historically speaking, but because these pieces of evidence seemed wrapped up in the controversy, he gives the evidence and its subsequent argument.
While I do not mean to denigrate the efforts of historians, as a scientist-in-training I personally think that the interest in those controversial events lies not in the exact truth of them, but rather in the ethical implications attached either way. If this book can be said to have a theme outside of the main subject matter, the "ethics of science" is the most prominent. This is far from surprising, as World War II really encompasses that question as a whole. I honestly don't think the question was considered before the fall of Nazi Fascism and the bombing of Hiroshima and Nagasaki. However one falls on the question of ethics, the life of Heisenberg is an excellent first stepping stone for addressing the intersection between ethics and science, and as such, this is a book any scientist (or ethical philosopher) ought to be interested in reading.