I recently listened to the audiobook version of The Billion Dollar Spy by David E. Hoffman. This is a non-fiction book that reads like a thriller, mostly relating to the recruitment and running of Russian spy Adolf Tolkachev at the height of the Cold War. Tolkachev was an engineer with access to vital secrets, and for years he operated right under the nose of the KGB. Much of the information he provided related to aircraft radar and air defenses, making it somewhat personal for me - as an Air Force pilot, the combat zones I flew in were safer thanks to Tolkachev.