I need something that's not too long and preferable something that makes you think. I'd like to shy away from science fiction or fantasy for this.

Charles Bukowski - Ham On Rye (or anything else from him)
Jack Kerouac - On the Road
Milan Kundera - The Unbearable Lightness Of Being
Paul Auster - The New York Trilogy
T. C Boyle - Drop City
Franz Kafka - Metamorphosis
Salinger - Catcher in the Rye
Brett Easton Ellis - American Psycho

If you want something long, but worth it:

Fjodr Dostojewsky - Crime & Punishment

Sci-Fi that makes you think:

Anything from Philip K. Dick
Stanislaw Lem - Solaris

I could give you more recommendations when I'm at home. Don't remember everything my book shelf has to offer

Anything Tom Clancy

the Netforce Series

I'd like something that could be read in concert with another person. I was thinking about the Unbearable Lightness of Being.

How do you mean that? "in concert"?

Mhm, it's a good book. You should check out Bukowski too tho, I can also only recommend his short stories (most people say they're even better than his novels).

A Short History of Nearly Everything

Yea I gotta do like a corespondance with anotherperson who is reading the same book.