John le Carre's novels may not be the breeziest examples of beach reading, but his most engrossing TV and film adaptations also require shifting your brain out of idle:
"The Spy Who Came in From the Cold" (1965): Richard Burton mines all his hard years of drinking and carousing to inhabit Alec Leamas, a walking corpse who has a tough time hanging up his cloak and dagger.
"Smiley's People" (1982): Alec Guinness provides a master class in subtle acting as an agent pulled out of a retirement home for a rousing round of international shuffleboard.
"The Tailor of Panama" (2001): Bond veteran Pierce Brosnan inhabits a totally different kind of spy, one with more ambition than loyalty, destroying a heartbreakingly vulnerable Geoffrey Rush in the process.
"Tinker Tailor Soldier Spy" (2011): Not nearly as long — or engrossing — as the 1979 miniseries, but it provides a showcase for a wide range of British actors including Gary Oldman, Tom Hardy, Colin Firth and Benedict Cumberbatch.
"A Most Wanted Man" (2014): An extra layer of melancholy lies over this already downbeat tale of an illegal immigrant caught in a war on terrorism as it marks one of Philip Seymour Hoffman's final performances.