Completely off what I am pleased to imagine is my topic...over at MR Tyler Cowen has invented a game - "seminal books of each decade". I agree with only one of his eight choices (yes, I'm sure he's bothered) so thought I'd call it a game. The point is not to pick the book from each decade that you think best, but the ones with the greatest cultural significance. Incidentally I think The Great Gatsby an odd starting point and my pick for the 1920s would be one of the Wodehouses - any of the Jeeves or Psmiths would do just fine.
Anyone can play, should it amuse you to do so.
1940s: Brideshead Revisited
1950s: The Lord of the Rings (I don't even much like LotR, but can't see how it's cultural significance is matched by anything else much written in English in the C20th)
1960s: Catch 22 (the single point of agreement between me and MR)
1970s: Fear and Loathing in Las Vegas (with a very strong second place for Hitch Hiker's Guide to the Galaxy, but I shouldn't pretend that all of the really important books of the C20th were science fiction, however much my own tastes say so)
1980s: A dead heat between Neuromancer and Watchmen, both of which are unusually definitive markers of the rebirth of their respective genres as serious cultural influences
1990s: Harry Potter - any of them would do but to my mind the strongest novel is the first one, and they get gradually slightly worse thereon. Harry Potter will, I think, turn out to have been a complete one-off as a cultural and publishing phenomenon
2000s: I rather fear it was the Da Vinci Code, which everyone read, eventually even people who should have known better, merely because they wanted to know what the fuss was about. I am proud to say I did not. It stayed in the top ten books for three sodding years, I believe a record. Or possibly it was Twilight, for which ditto apart from the three years bit and the me not reading it bit (whoops). I would have liked it to be Mick Foley's Tietam Brown, which was the first great American novel of the new millenium (and not that drivel by Frantzen which is commonly accorded this accolade) but no-one read Tietam Brown. Alas, alas.
The game seems to imply "in English" or maybe "within the English speaking world" - otherwise Mao Zhedong's Little Red Book, Mein Kampf and maybe Zabibah and the King (hee hee) should maybe make the list.