Canaris: The Life and Death of Hitler's Spymaster is a highly detailed, very nuanced biography of the enigmatic chief of the Abwehr during the Nazi regime, authored by a German journalist who has written several books on the German intelligence services. 

The book reveals Canaris as a complex individual who is never quite what he seems to be, or, perhaps more accurately, what historians and biographers have attempted to make him out to be.  Mueller gives us glimpses of Canaris as enthusiastic supporter of the Nazi regime, as dissident, as nationalist, perhaps even traitor, at the end, as conspirator.  But perhaps above all else, he shows Canaris as a man who preferred to be something of a mystery, hinting at a family and personal history that was, in fact, not necessarily very accurate, and a masterful bureaucratic in-fighter with his own agenda. 

This book is likely to become the standard treatment of Canaris' life and career.