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
David Benioff, City of Thieves
Richard Flanagan, The Narrow Road to the Deep North
Richard Price, The Whites
Patrick deWitt, The Sisters Brothers
John Burdett, Bangkok Eight
Neal Stephenson, Quicksilver, The Confusion, The System of the World
John Nichols, The Milagro Beanfield War
Zane Grey, Riders of the Purple Sage
Cormac McCarthy, Blood Meridian
Don DeLillo, Underworld
Elmore Leonard's gangsta stories
Frank Lentricchia's gangsta stories of northern New York
Hilary Mantel, Wolf Hall, Bring up the Bodies, The Mirror and the Light
Anton Gill's Egyptian detective stories: "City of …" [best read in sequence]
Anthony Doerr, All the Light We Cannot See [best novel of the last 20 years]
Arturo Perez-Reverte, What We Become
Peter Carey, The Chemistry of Tears
David Mitchell, Black Swan Green
Colum McCann, Zoli
Ian McEwan, Sweet Tooth, Solar
David Liss, A Conspiracy of Paper
Iain Pears, The Dream of Scipio
Umberto Eco, The Name of the Rose
Thomas Keneally, Napoleon's Last Stand
Ken Follett, Fall of Giants, Winter of the World
Bernard Cornwell's Saxon Chronicles [best read in order]
Jay Newman, Undermoney
Jonathan Lethem, As She Climbed Across the Table
Natasha Pulley, The Kingdoms
Steve Almond, Against Football [One Fan's Reluctant Manifesto]
Tania James, Atlas of Unknowns
Rachel Kushner, Telex from Cuba
Erin Somers, Stay Up with Hugo Best
John Banville, Doctor Copernicus, Kepler, The Newton Letter
Benjamin Black's [Banville's nom de plume for detective stories] Quirke series
Flann O'Brien, At Swim Two Birds
J.P. Donleavy, The Ginger Man
Thomas Flanagan, The Year of the French
Thomas Pynchon, Gravity's Rainbow
James Clavell, Shogun
Frank Herbert, Dune [not its sequels]
Richard Condon, An Infinity of Mirrors
Anthony Burgess, Earthly Powers
Salman Rushdie, The Enchantress of Florence
Shakespeare-iana:
Sally O'Reilly, Dark Amelia
Maggie O'Farrell, Hamnet
Maria Duenas, The Time in Between