Tyler Cowen lists the best book each decade since the 1920's:
1930s: The Grapes of Wrath, John Steinbeck.
1940s: Farewell, My Lovely, by Raymond Chandler.
1970s: This is tough. There is Vonnegut’s Breakfast of Champions, Stephen King, and even Peter Benchley’s Jaws. I’ll opt for Benchley as a dark horse pick, note that these aren’t my favorites but rather they must be culturally central. Jonathan Livingston Seagull is another option, as this truly is an era of popular literature.
1980s: Tom Wolfe, The Bonfire of the Vanities.
2000s: Malcolm Gladwell, The Tipping Point.