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This list isn't complete, scholarly, or recommended by anyone except myself. These are some of the books that have guided my thinking and helped me arrive at what I believe in today. So be that as it may, and with the reader officially warned, here are my personal recommendations in no particular order.
Mothernight by Kurt Vonnegut
From an Amazon.com  reviewer:
'While he [Howard Campbell, the protagonist] is reviled by almost everyone on earth as an American Nazi traitor, the truth is that he was actually an agent working for the American government during the war; this is a truth he cannot prove, though. Thus, in this 1961 novel, the hero is ostensibly a Nazi war criminal. The moral of Mother Night, Vonnegut tells us in his introduction, is that 'we are what we pretend to be' and should thus be pretty darned careful about what we are pretending to be.'
I couldn't have put it better myself, so I didn't try to.
I really liked Vonnegut's sci-fi and short story anthologies that I was introduced to by friends in high school. I came across Mothernight by accident. I think that of all the philosophically themed novels I have ever read, it had the most influence for me on the role of honesty, rationality, and truth in man's life.
The Law by Frederic Bastiat
While some aspects of economics are incompletely dealt with, Bastiat's defense of free markets, a minimalist state, and the proper role of the law and legislation in a society, (i.e. to protect individual rights and property), is simply one of the best of its kind ever written.
The Law is short, easy to read, and makes its points directly and logically, and so for me was a great read. The task of slogging through a thousand page or multi-volume treatise on political economy or philosophy may get major wood for poli sci grad students, politics junkies and such, and if that's your thing, cool. However, my attention span is too short for all that. And I prefer to live my life rather than read about how to live it to devote that much time to the more verbose writers.
Homage to Catalonia by George Orwell
In the 1930's, fascism seemed to be swallowing up Europe . Hilter, Mussolini, Stalin, and Franco were the major figures of the day. The war for Spain was between a coalition, which ranged politically from anarchists to royalists, versus a rebellious army junta that wanted to impose Mussolini-style fascism.
Assorted private individuals from around the world traveled to Spain and enlisted in one or another  of the various military branches of the anti-fascist coalition. Orwell enlisted as a private in an anarchist militia unit. He served as an infantryman in combat for over a year until he took a rifle bullet through the throat.
Orwell was proudly a 'man of the Left' but who never feared to honestly call things as he saw them even if it pissed off his nominal allies who thought Stalin and the Communist International were the best things invented since sliced bread.
Snowcrash  by Neal Stephenson
Snowcrash is a sci fi novel premised on what Stephenson thinks an anarcho-capitalist  society might be like. Both good and bad too. He writes a story that is at once piquant, hilarious, creepy and inspiring, all at the same time.
Anthem by Ayn Rand
Of all of Rand 's novels, Anthem is easiest to read. As some Rand scholars have noted  Miss Rand was an American writer who was educated in and of the tradition of the Russian Silver Age . The Silver Age has been described as the last great era of Russian culture before Stalin and the Soviet State destroyed Russian culture entirely attempting to create a Communist-directed hive mind society. But also meaning way too lengthy novels featuring rather stunted, one-dimensional characters. For example, this little snippet from Anthem:
'I need no warrant for being, and no word of sanction upon my being. I am the warrant and the sanction.'
Pithy, concise and very well put. Too bad she couldn't trim down some of John Galt's  soliloquies to something along those lines, eh? But I digress.
If you can't hack through The Fountainhead or Atlas Shrugged, try Anthem. It isn't 'Ayn Rand Lite,' just Ayn Rand concise, and that is a distinction with a major difference.
If you hated my choices listed here, well, too bad. If you disagree or want to inform me of some others that you like or liked better than mine, send me an email and I'll get back to you.