That is a fascinating book. To put it into context one should also read this (which I think has already been recommended in this thread):
Live and Let Spy: BRIXMIS: The Last Cold War Mission by Steve Gibson.
The "Reflections" section in later editions, added by the author many years (around 2011, I think) after initial publication is absolutely fascinating and a very good precis analysis of the state of the World then and today; it goes far beyond discussing BRIXMIS.