My second book for this challenge was truly a "fill in the gap," because I don't recall ever reading a spy novel before. It was enjoyable, but I wouldn't want a steady diet of the genre. The Spy Who Came in from the Cold is said to be one of the best, probably because of its unvarnished commentary on the evils of espionage and similar dark deeds in the name of national defense. This is a message told forcefully and convincingly. My full review is here.