As with wine, life is too short for bad literature. Here are some very good reads:
Spy Thrillers:
Alan Furst, Dark Star
Martin Cruz Smith, Havana Bay, Gorky Park, Polar Star
Philip Kerr, March Violets, Pale Criminal, German Requiem
John Le Carre', A Call for the Dead, Absolute Friends
Edward Wilson, The Envoy
John Lawton, Then We Take Berlin
Eric Ambler, A Coffin for Dimitrios
Chris Pavone, The Expats
David Downing, Zoo Station
Joseph Kanon, Istanbul Passage
Jason Matthews' Red Sparrow, Palace of Treason, The Kremlin's Candidate
Olen Steinhauer, Bridge of Sighs
Robert Harris, Archangel, the Cicero trilogy: Imperium, Conspirata, Dictator
Charles Cumming, A Spy by Nature, The Spanish Game
Keith Thompson, Once a Spy, Twice a Spy
Martin Booth, A Very Private Gentleman
Daniel Silva, The Cellist
William Maz, The Bucharest Dossier