Subtitled "The Greatest Spy Operations of the 20th Century," which pretty much sums up the book.
Volkman has selected 22 cases, and devotes a good chapter to each. He covers how the operations began, their objectives and their effects on history. His writing is good, making even a few of the more dry cases interesting. Most of them don't need this, as they're pretty exciting. There's also a large number that I knew nothing or very little about.
He rounds it off with perhaps the most ludicrous operation ever, an attempt in 1945 to reduce German morale using forged postage stamps with subversive messages on them. Yes, really. (Spoiler: it had absolutely no effect on German morale).