1. The Law - Frederic Bastiat
2. Economics in One Lesson - Henry Hazlitt
3. Why Government Doesn't Work - Harry Browne
Those 3 oughta set anybody straight
These might be better intro books for some:
The Politically Incorrect Guide to American History - Tom Woods
Myths, Lies, and Downright Stupidity - John Stossel
1. For a New Liberty: The Libertarian Manifesto by Murray Rothbard
2. Healing Our World in an Age of Aggression by Mary Ruwart
3. Atlas Shrugged by Ayn Rand
4. The Market for Liberty by Morris & Linda Tannehil