Just finished "The Double Cross System" by JC Masterman.
All about the activities of the XX Committee in WW2 that ran a network of double agents to feed the Germans false information.
The Abwehr thought they had a good spy network in the UK; in reality the British controlled everything.
The most celebrated agent was "Garbo" who played a big part in the D-Day deception plan (Operation Fortitude).
Now reading "Dark Sun" by Richard Rhodes which is about the development of the hydrogen bomb.
First part focuses on how the Soviets got their own atomic bomb with a lot of help from their spies at Los Alamos.