The Billion Dollar Spy gets at the crushing paranoia of running intelligence operations at the height of the Cold War in Moscow, right under the nose of the KGB. Adolf Tolchakev was a Russian radar engineer who had grown disenchanted with the Soviet Union, a country that crushed liberty and failed to provide for its people. This middle aged engineer with impeccable credentials began passing notes into the windows of American diplomatic cars (by chance his first target was a CIA officer and not an actual diplomat). It took years for the CIA to decide that Tolchakev was for real, and not a KGB gambit.

They provided cameras, and Tolchakev delivered thousands of page outlining the latest in Soviet R&D for radars, especially high-tech look-down/shoot-down designs which would give Soviet interceptors much better odds against the American bomber fleet. The US Air Force estimated the value of Tolchakev's intelligence as billions of dollars saved in R&D costs.

This book has two themes. The first are the Moscow Rules and operating "in the black". Americans in Moscow were routinely followed by the KGB. Any meetings with agents or transfer of items by dead drop had to be proceeded by breaking surveillance, going black in CIA parlance. Where the Mendez' book Moscow Rules presents this as sleight of hand, entertaining war stories, Hoffman focuses on the isolation and paranoia that agents experience. You could never know if you were clear, and failure would mean the arrest and execution of your agent.

The second is the psychological pressure of being a spy. In being a case agent is hard, being a spy is much harder. Most agents are abnormal in some ways, and the CIA had to balance Tolchakev's demands for cash, a suicide pill, and then consumer goods and medicine only available on the black market, with their fears that he would be unable to explain where the money or goods came from, or take the pill in a moment of weakness. But Tolchakev's desire to hurt the USSR, inspired by dissident physicist Andrei Sakharov and defector MiG-25 pilot Viktor Belenko drove him to stay on the job.

I avoided googling anything from this case, because I hoped that Tolchakev would make it out alive, but he was down in by betrayal from within the CIA, as two officers turned traitors, Edward Lee Howard and Aldrich Ames, turned over information revealing a high level source in the radar institute. The KGB was able to identify Tolchakev as the source, and he was arrested and executed. I've read a fair number of books on the spy game, and this is one of the best.