Physics and philosophy
I found two main threads in the book. The first is the relationship of quantum theory with earlier science and philosophy. Heisenberg starts with a history of the development of quantum theory up to 1927. He then looks at the early ideas the Greeks had concerning atomism and the nature of matter, and moves on to the ideas of philosophers such as Descartes and Kant. He goes on to explain how quantum theory allowed chemistry to be explained in terms of physics, and discusses whether biology is likely to follow a similar path.
The second thread of the book is how difficult it is to understand quantum theory in terms of what had gone before. Although Einstein's relativity was a challenge, quantum theory is something else again, and maybe it even needs a new type of language to talk about it. Heisenberg supported the Copenhagen interpretation, which he describes and goes on to defend against some of the competing interpretations. However, I din't feel his defence was very strong - he used rather dubious logic to argue that competitors were just trying to return to classical physics. In fact my impression was that Heisenberg was really a 'shut up and calculate' man.
In the final chapter Heisenberg takes a wider view, discussing topics such as how traditional cultures will be affected by science as well as giving his views on the spread of atomic weapons.
A lot has happened in the philosophy of physics in the half century since this book was written, but I think it will still be of interest to many readers, firstly those who want to know more about Heisenberg and his thoughts, and secondly to those wanting to find out about the state of the Copenhagen interpretation at a time when it was beginning to be seriously challenged by other interpretations.