["The Rhinemann Exchange" is an] espionage thriller set in the desperate last year of the Hitler war. The situation that ignites the action (nearly five hundred sanguineous pages of it) is preposterous but intellectually undemanding. Germany has perfected a gyroscopic airplane-guidance system but lacks the industrial diamonds needed to complete its terrible rocket missile; the United States has access to tons of industrial diamonds but its aerophysicists can't get the kinks out of its top-priority gyroscope. So a corrupt military-industrial cabal on both sides agrees to a secret, treasonous exchange, and Rhinemann, a German Jew (an "expatriot," in the author's vocabulary) living in Buenos Aires, is selected to handle the transfer. The United States, being no fool, sends a top agent, Captain Spaulding (Groucho Marx may be amused to learn), to Buenos Aires to look after its interests but (as is classically customary in spy stories) refrains from...