Classic
The list of what Reddit considers the "classics". This is pretty much the books that appear on a lot of the other lists.
The Great Gatsby by Fitzgerald
Ender's Game, Book 1: Ender's Game by Card
The Things They Carried by O'Brien
Things Fall Apart by Achebe
The Grapes of Wrath by Steinbeck
Slaughterhouse Five by Vonnegut
Of Mice and Men by Steinbeck
World War Z by Brooks
Their Eyes Were Watching God by Hurston
To Kill a Mockingbird by Lee
Catch-22 by Heller
A Tree Grows in Brooklyn by Smith
Infinite Jest by Wallace
Lolita by Nabokov
The Ultimate Hitchhiker's Guide to the Galaxy by Adams
Brave New World by Huxley
Cat's Cradle by Vonnegut
House of Leaves by Danielewski
A Confederacy of Dunces by Toole
The Catcher in the Rye by Salinger
Zen and the Art of Motorcycle Maintenance by Pirsig
Animal Farm by Orwell
Blood Meridian by McCarthy
Snow Crash by Stephenson