The Citizenship Papers by Wendell Barry. Profound reading.
Stiff by Mary Roach. Cadavers do indeed have fascinating stories.
The Elegant Universe by Brian Greene. Blows my mind.
Cosmos by Carl Sagan. A classic of epic proportions.
Walden by Henry David Thoreau. Wonderful, impassioned.
Complications by Atul Gawande, MD. I'm a future doctor, but I bet everyone could benefit from reading this well-written book.
The Social Transformation of American Medicine by Paul Starr. The definitive work on the subject, and very germane to today's health care troubles.
The Last Intellectuals by Russell Jacoby. Intensely fascinating.