So far, I'm semi-firm on the following works:
"Sestina: Altaforte" by Ezra Pound (1909)
A Farewell to Arms by Ernest Hemingway (1929)
"Gerontion" by T. S. Eliot (1920)
"The End of the World" by Archibald Macleish (1926)
"In Distrust of Merits" by Marianne Moore (1944)
Slaughterhouse Five by Kurt Vonnegut (1969)
The Crying of Lot 49 by Thomas Pynchon (1966)
Do Androids Dream of Electric Sheep? by Philip K. Dick (1968)
I'm considering the following:
Urinetown (text) by Mark Hollmann and Greg Kotis (2001)
"I Have No Mouth, and I Must Scream" by Harlan Ellison (1967)
"They're Made of Meat" by Terry Bisson (1991)
Starship Troopers by Robert Heinlein (1959)
Ubik by Philip K. Dick (1969)
"Fates Worse Than Death" by Kurt Vonnegut (1982)
"Dutchman" by Amirir Baraka (1960)
"Almost Browne" by Gerald Vizenor (1991)
"Entropy" by Thomas Pynchon (1984)
"Neo HooDoo Manifesto" by Ishmael Reed (1972)
"Holy the Firm" by Annie Dillard (1994)
I'm trying for a mix of poetry, short stories, and novels (with a play). Long novels are basically out, though, since I can't justify devoting time to anything significantly over 250 pages.
There is also another problem here: while there are a few women writers in the poetry and short fiction genres, most of my selections are by men. To be fair, most of the works I'm interested in are from the 1920s to the 1960s, which means that a great deal of those works we might call "classic" are by men, but this still leaves me feeling uncomfortable. Who am I missing other than Toni Morrison (who I can't stand)? I must admit that outside of the SF/F genres, I am ignorant of female writers of significant works of fiction in the U.S.
So, that's where I'm at right now. If you have suggestions of books you love, whether SF/F or not, feel free to leave a comment.