I didn’t know if I should put this here, in IMHO, or in GD. If this is the wrong place, or if it look suited to move somewhere else later on, hopefully a nice mod will come along and give this thread a home. In the meantime… what books do you think everyone should read and why?
I’ll start with the obvious.
The Old and New Testamants - Not because I’m trying to convert anyone, but because they’re two of the most important works of literature ever put to paper. Allusions and references are seeded throughout literature of all kinds. If you don’t know these books, you’re in the dark.
The Screwtape Letters - CS Lewis.
Because it’s very funny, and because the man’s mind was like a razorblade.
The End of the Affair by Graham Greene, and Lolita by Vladimir Nabokov, to truly understand what passion in love is.
On a somewhat different tack, I highly recommend How to Lie with Statistics by Darrell Huff. Written in the 1950s, so some of the numbers are outdated, but vital reading for every educated person.
Sun Tzu-The Art of War
Martin Luthur King - Strength to Love
J D Salinger- Catcher in the Rye
Joseph Heller - Catch 22
Read the Dictionary: it has all the words and is therefore equivilant to reading all books. 
The Seven Pillars of Wisdom - T.E. Shaw (T.E. Lawrence)
Go Rin No Sho (The Book of Five Rings) - Myamoto Musashi
Black Elk Speaks (Being the Life Story of a Holy Man of the Oglala Sioux) - Black Elk
War of the Worlds - H.G. Wells
Animal Farm - G. Orwell
The Demon-Haunted World by Carl Sagan. Should be required reading in high school, IMO.
Second on The Demon-Haunted World.
At the risk of throwing this thread into Great Debates, I’ll nominate Lies and the Lying Liars Who Tell Them, because it’s the only current-events book that (a) has facts and claims that have stood up to everything its critics tried to throw at it, and (b) is easily digested for even casual readers.
And how come nobody’s said The Straight Dope yet?
1984 and Brave New World, both of which are rife with today’s problems expanded out to their potential (disastrous) proportions.
And I second the Old and New Testaments, and raise you a Qu’ran.
You could try these:
**
Old Testament
New Testament
Odyssey
The Republic
King Lear
Hamlet
Don Quixote
Paradise Lost
Songs of Innocence and Experience
1984**
Green Eggs and Ham: a) because it holds an important lesson, b) because it is fundamentally silly, and C) because Dr. Seuss, world’s greatest children’s author, was neither a doctor, nor did he have children, which somehow tickles my irony bone.
To Kill a Mockingbird: because we should all try to be a little more like Atticus Finch.
The Religions of Man, by Huston Smith: because it is the clearest introduction to the subject of religion I have read, and it bubbles with the wonder and passion that underlies any belief system.
Shot in the Heart by Mikal Gilmore
Guns, Germs, and Steel by Jared Diamond
Dominion by Matthew Scully
I’d recommend Harper Lee’s To Kill a Mockingbird to everyone if they haven’t read it already.
Farenheit 451, of course!
Gilgamesh (oldest book known)
Brave New World
The Jungle
…and a lot of others that have already been pointed out
other than some of the ones already mentioned:
Saving the Appearances - Owen Barfield
Either/Or - Soren Kierkegaard
The Dimensional Structure of Consciuosness - Samuel Avery
The Great Divorce & 'Till We Have Faces - C.S. Lewis
The Lord of the Rings - J.R.R. Tolkien
Everyone should read Les Miserables. At the very least they should read the abridged version. It has so many lessons about humanity, and the world around us. On top of that Victor Hugo is one of the most eloquent authors I’ve ever read.
Hell, even Ann Rand praised him, and she thinks altruism is the world’s greatist evil.
forgot to add some science books
Gödel, Escher, Bach: An Eternal Golden Braid - Douglas R. Hofstadter
A Brief History of Time - Stephen W. Hawking