Lamb by Christopher Moore, 1984 by George Orwell, A Brave New World by Aldus Huxley, God Is Not Great by Christopher Hitchens, Lord of the Rings by J.R.R. Tolkien... Not in that order, lol

The Golden Notebook, Sing Buried Sing, Pride and Prejudice, Great Expectations, and The Tin Drum. Of course five just aren't enough.

Sense and Sensibility by Jane Austen. The Stand by Stephen King. Breakfast of Champions by Kurt Vonnegut. Dune by Frank Herbert. The Mists of Avalon by Marion Zimmer Bradley.

Fiction: John Connolly's Charlie Parker series.
The Jungle, Upton Sinclair.
Johnny Got His Gun, Dalton Trumbo.
Into the Forest, Jean Hegland.
Revenge and Legends of the Fall, Jim Harrison. ( they are short and I could not choose one).
Honorable Mention: Zen and the Art of Motorcycle Maintenence, Robert Praising. The Source, James Michener
Non Fiction:
Dreaming The Dark, Starhawk.
Spritual Midwifery, Ina May Gaskin ( what can I say, I'm a Midwife).
The Mind's Sky, Timothey Ferris.
A People's History of the United States, Howard Zinn.
The Last Drop of Ancient Sunlight, Thom Hartman.

                     So many books, so little time. I got a little carried away, but this is nearly impossible for me to narrow down.

Shogun, by James Clavell
East of Eden, by John Steinbeck
The Butcher's Boy, by Thomas Perry
The Persian Boy, by Mary Renault
I, Robot, by Isaac Asimov

I read the other books recommended by others here and chose to recommend books other did not to increase varities and titles.

Catch-22
On the road
One flew over the cuckoos nest
Fear and loathing in Las Vegas
A short history of nearly everything

Some of my favorite Authors: Terry Brooks & Terry Goodkind....so most of their books if you like fantasy.
God is Not Great. Hitchens
Sense & Goodness without God and On the Historicity of Jesus. Richard Carrier
Kiss me like a stranger. Gene Wilder

Razors edge, world according to garp, on the road, ullysses, zen and the art of motorcycle maintainance

How about some modern fiction (in no particular order):

• The Wasp Factory, Ian Banks
• House of Leaves, Mark Danielewski
• The Forever War, Joe Haldeman
• John Dies at the End, David Wong
• Exquisite Corpse, Poppy Bright

Jonathan Livingston Seagull by Bach, The five people you meet in heaven by James Ablom, The Prophet by Kahill Gibran, Winnie the Pooh by A.A. Milne, and my all time favourite The Hobbit By J.R.R. Tolkien.
As a side note where a few of these books may in fact seem to be on a religious slant it does not preclude them from being good books they are however fiction with life lessons one may choose to read into, or not!
I found each for their own reasons to be insightful, as well as just allowing me to use my imagination allowing me that good does triumph in the end!

Madeline Miller's Song of Achilles, Alex Haley's Life of Malcolm X, Autobiography of B.B. King, Autobiogrpahy of Morton Downey Jr, Romance of the Three Kingdoms

Complete works of H.P. Lovecraft, C.S. Lewis, Michael Crichton. Archie Fire Lame Deer The life of a Dakota Medicine Man & World of Warcraft novels.

Epic of Gilgamesh, The Illiad, The Odessey, Complete works of Edgar Allan Poe, The Battle of Middle Earth by J.R.R. Tolkien tied with The complete works of George R. R. Martin, creator of Game of Thrones