The Fountainhead or Atlas Shrugged are both great by Ayn Rand but they are very long.
See, I agree with the Fountainhead but for some reason have never been able to get into Atlas Shrugged. I may have to read it again sometime.
Some Books That I'd Recommend:
Flowers for Algernon by Daniel Keyes
Hitler: The Pathology of Evil by George Victor
and I'm currently reading
What If? 2 which is a collection of essays on historical events that reimagines something being changed (Socrates dying in battle before his philosophy passed on, Pontius Pilate sparing the life of Christ, Martin Luther being sentenced to death by the Diet of Wurms, etc..). I found it at a Barnes and Noble store for like $5 (I dearly love their cheap displays up near the front).