Unfortunately, I don't know the specific 8 spy novels from The Economist. However, one of the most popular spy novels is 'Eye of the Needle' by Ken Follett. It has a great plot that keeps the readers on the edge of their seats. It involves a German spy during World War II.
Sorry, without access to The Economist's list, I can't give you the exact 8. But 'The Manchurian Candidate' by Richard Condon is a classic spy novel that has been made into a movie. It explores themes of brainwashing and political intrigue. It's a story that really makes you think about the power of manipulation in the context of espionage.
I'm unable to list the 8 from The Economist. But a good spy novel is 'Our Man in Havana' by Graham Greene. It's a satirical take on the spy genre. It shows how a vacuum - cleaner salesman in Havana gets involved in the world of espionage in a rather comical yet thought - provoking way. It also delves into the absurdities of the Cold War politics.