Do you mean fiction? Non-fiction? Subject area?
For me, generally:
* Your Money or Your Life - Joe Dominguez (MUST READ)
* Is the American Dream Killing You? - Paul Stiles (MUST READ)
* Working Ourselves to Death - Diane Fassel
* Wind in the Willows - Kenneth Grahame (esp. the chapter The Wayfarer)
* The Hobbit - Tolkien
* The Hunt for Red October - Tom Clancy (amazing level of technical detail)
* 1984 - George Orwell (published in 1949 but never been more relevant)
Have fun!