The book that hit me next and hardest was "Starship Troopers" by Robert Heinlein.
I first read it when I was a very impressionable 14-year-old, toddling into the age of reason.
The idea that hit me hard was that morals could be understood as prudence. So, for me, moral reasoning became a radically cool very-interactive counter-cultural activity, more like designing one's life than like mindless submission to authority.
My schools had _no_ moral instruction at all ! The "preachiness" and
"worthless didactic fluff that does not advance the plot" and
"hard-headed militarism" were _exactly_ what I found most valuable in
"Starship Troopers". (Those are paraphrases of critics- see any Heinlein
site on the web)
After that, it took me years to find out where the rest of the good stuff was hiding out. I made a lot of life mistakes because everybody I knew, including librarians, was too ignorant of the classics of Western Civ to tell me to read them.
I read Proverbs. This is just as thought provoking as Heinlein, and maybe even more subversive, if one examines the rules as prudence. Likewise Deuteronomy. Try reading these in concert with Dawkins' "The Selfish Gene" and "Sociobiology" for a real treat.
I've read all of Plato and most of Aristotle, and I think the Republic and Laws are also pretty cool, again for the same reasons. Western law's theory of justice came from Plato's Laws, which were proposed as a model of practical law. The Republic describes a very smart man's carefully-considered perfect government. The obly problem I found is that it doesn't cope with population growth.
Aristotle's "Nicomachean Ethics" sets the terms of the debate: "How then Should we live?" and then eliminates the obvious, foolish answers.
Montesquieue's "Spirit of the Law" ("L'Esprit de Loi")is an attempt to explain, generalize and repair Plato's Republic. The writers of the U.S. Constitution read it most carefully. Most of it is nonsense, but he invented the answer to whom should guard the guardians. Read it in the french version if you can: the author answers his clerical critics from the security of the grave. However, the English version was corrected by him while he was still alive.
The next big jump forward is probably Jeremy Bentham's "Principles of Morals and Legislation" which is as dry as dust, but tries to fix the subjectivity of Plato's "The Laws," and which inspired Mill to write about "Utilitarianism" which is not dull at all
After that, probably Kant's "Foundations of the Metaphysics of Morals" was a glimpse of the promised land, because it gives one faith that somehow everything ties together. This was a less-flawed attempt to side-step Aristotle's problems.
G.E. Moore's "Principia Ethica" was a bitter dose of skepticism with a fairy story at the end. It sets the current state of the art in skepticism about Ethics.
I think everyone should read Das Kapital, by Marx, not for the fallacious theory of value, but for the deadly-accurate analysis of classical capitalism, and the clear exposition of dialectical theory. His theory of history, incidentally, is right on. and accurately described the pressures on the system. The revolution came and went, unnoticed because it was accomplished by incremental reforms through democratic institutions. Evaluated by the Communist Manifesto, the U.S. is a practical socialist state: Every socialist reform in the Manifesto is implemented in the U.S
I think everyone should read Toynbee's "The Rise and Fall of the Roman Empire," and Plutarch's "Lives" These are the alphabet of history and biography.
Kipling's stuff, and the Lays of Ancient Rome are incredibly cool, once one knows enough history to make sense of them. They got me to read history.
Everyone should read an encyclopedia article about accounting. Especially notice the date when double-entry accounting was invented, and how it immediately preceded (enabled) both the industrial revolution, and the internecine wars of the 15th .. 20th century in Europe.
David Friedman's "The Machineries of Freedom" liberated me from mindless advocacy of government. It should be read with "The Enterprise of Law" an economic analysis of law that explains why radical libertarian systems failed historically.
The federal reserve published a book to explain to laymen about why it exists, and what purposes it serves. It should be read in tandem with Bastiat's book (Called "The Law" I think) about the historic failures of central banks.
The Federalist papers are the design notebook of the U.S. constitution. They should be read with a rational criticism of the U.S., such as "The Frozen Republic".
After that, probably Dawkins' "The Selfish Gene" and E.O. Wilson's
"Sociobiology" helped me to think more carefully about how we should
live.