David Langford's Top 20

This is a top 20 list that excludes books written after 1989:

20) Terry Pratchett, Guards! Guards! (1989)
19) Frederik Pohl: Gateway (1977)
18) Iain M. Banks, Consider Phlebas (1987)
17) C.J. Cherryh, Cyteen (1988)
16) Barry Hughart: Bridge of Birds (1984)
15) Christopher Priest, The Affirmation (1981)
14) Roger Zelazny, Lord of Light (1967)
13) Philip K. Dick, The Three Stigmata of Palmer Eldritch (1965)
12) Alan Garner, The Owl Service (1967)
11) Alfred Bester, The Stars My Destination (1956, alias Tiger! Tiger!)
10) Algis Budrys: Rogue Moon (1960)
9) Greg Bear, Blood Music (1985)
8) Frank Herbert: Dune (1965)
7) Mervyn Peake: Gormenghast (1946-59)
6) Ursula Le Guin: Earthsea (1968-72)
5) Keith Roberts, Pavane (1968)
4) J.R.R. Tolkien: The Lord of the Rings (1954-55)
3) Arthur C. Clarke: The City and the Stars (1956)
2) John Crowley: Little, Big (1981)
1) Gene Wolfe: The Book of the New Sun (1980-83)

Ones I've read are in bold print. The list is annotated on this page with explanations and descriptions.

He also has a list of "Good Stuff Since 1990":

1990: Dan Simmons, Hyperion Cantos
1991: Pat Cadigan, Synners
1992: Kim Stanley Robinson, Red Mars
1993: Michael Swanwick, The Iron Dragon's Daughter
1994: Greg Egan, Permutation City
1995: Stephen Baxter, The Time Ships
1996: Mary Doria Russell, The Sparrow
1997: Tim Powers, Earthquake Weather
1998: Avram Davidson and Grania Davis, The Boss in the Wall
1999: Vernor Vinge, A Deepness In the Sky
2000: China Miéville, Perdido Street Station

Again, ones I've read are in bold print.

There are several books from both of these lists that I have been on the look-out for at my favorite used book store, but I may have to give that up and try another source. I think some of them are out of print.