re: Top 25 Most Iconic American Literature

The Sun Also Rises
Absalom, Absalom (I would also take As I Lay Dying instead or even The Sound and the Fury)
Run, Rabbit
Moby Dick
The Narrative of Arthur Gordon Pym
Catch-22
Slaughterhouse Five
Gravity's Rainbow
The House of Seven Gables/The Scarlet Letter
The Adventures of Huckleberry Finn
To Kill A Mockingbird
Invisible Man
The Great Gatsby

Those are the Pillars/Great Authors. After that, maybe throw in Atlas Shrugged or Philip K Dick for a touch of sci fi. I might also go with Frank Hebert's Dune. Then maybe something super modern like Snow Crash or House of Leaves or Ready Player One.

Then maybe Infinite Jest or Blood Meridian and something from Steinbeck.