Sutherland wrote several books about spies in Britain and is very knowledgeable about the circumstances of the defections of Burgess, Maclean and Philby. He writes beautifully and succinctly, and this look includes the discovery of Anthony Blunt as one of the Cambridge spies. However, he gives many cameos of the others that stay with one. I found this book useful in understanding the thinking of MI6 and MI5 during the period of questions about "The Third Man."
Gives a good insight into methods intelligence agencies use to compromise people for political gains. Other than that a good speculative fictional yarn.