A fantastic read. This is not for someone seeking detailed explication of Heisenberg's physics (the author deals with that more extensively in an earlier work). Rather it is a thorough and judicious investigation of Heisenberg's personal development, his roots in German society and culture and his consequent inability to abandon the country after the Nazis came to power. Heisenberg has often been accused of turning a blind eye, even actively colluding, with the Nazi regime. But this volume provides a necessary corrective to that superficial view. In fact he experience enormous difficulties with the Nazi bureaucracy, incessant and virulent attacks from the Nazi scientists Lenard and Starck, which at various times threatened to bring him down. It was ironically a dispute between warring factions of the Nazi bureaucracies - in which after long scrutiny he was supported by Himmler and his faction - that saved him. In circumstances where he chose to stick it out in his own country under often life-threatening pressure from a dictatorship, could he avoid or be blamed for his actions? Yes, he could have quit like Einstein (whose life admittedly was under threat), Schrodinger and others. But Cassidy shows why he did not and in not doing so that he did not choose the easy option. The later sections about Heisenberg's involvement with the Nazi nuclear bomb research are also interesting, although it turns out the Germans were far behind the US/British project and the Nazis swallowed the "theoretically but not technically feasible" assumption. It's clear that German scientists, including Heisenberg, were astounded by how far in advance their US/British counterparts were. The hubris of assuming German superiority in science, no doubt. The latter third or so of the book is dominated by this story, which therefore rather submerges other aspects of Heisenberg's life. The final chapter is a very rapid conspectus of Heisenberg's later years as a "public figure". Admittedly the source material may have been less voluminous. Or it may just be that after the excitement of the youthful discoveries (physics and math seems generally a young man's trade, pace Schodringer), inevitably the interest flags. To that extent the investigation of Heisenberg's role vis a vis the Nazis and the bomb project may make his life more revealing as a proxy for the scientist-ethics-society debate than those of most of his scientific peers. Cassidy is also particularly good on the historical background, something historians of science are not always so adept at. All in all, a well-written and highly recommended study of Heisenberg, his society, his place in quantum mechanics and his times.