A book?
A book? How about I name 10, in no particular order, and cut myself off there?
You'll find that I'm biased toward fiction. I don't believe there's any lesson about humanity that can't be taught more effectively and more interestingly by a talented fiction writer.
=====
The Analects of Confucius - There is an enormous amount of wisdom collected here. If you've never read this, you're really short-changing yourself. Fortune cookies got nothing on this.
The Bible - There is a lot of wisdom collected here -- the Sermon on the Mount alone -- and there is no one who won't benefit from understanding Christian scripture. This is almost certainly the most influential book ever written.
The Qur'an - Similarly, it is immensely valuable to understand Muslim scripture, particularly in the context of contemporary arguments about what is and is not religiously required of Muslims. The Hadith is a good idea for the same reason.
The Iliad - Apart from the Christian Bible, probably the most influential piece of literature ever written. Almost everything you've ever read was directly or indirectly influenced by this in some way.
All Quiet on the Western Front, by Erich Maria Remarque - The greatest war novel ever written, and the greatest novel of any kind I have ever read. No matter what you believe, it should change the way you think about war. If I really was picking just one book, this would probably be it.
The Lord of the Rings, by J.R.R. Tolkien - An accessible epic about love, war, and
the end of magic. A devastatingly effective parable its author always insisted wasn't really a parable. It's inspiring, depressing, fantastic, realistic, touching, heart-breaking, and substantially different than the movies. As a side note, I despise Peter Jackson. He is a shitty director, and I am not willing to allow for a difference of opinion on this. If you think otherwise, you're a fucking moron and I hope you choke on a celery stick.
The Seven Habits of Highly Effective People, by Stephen Covey - Mock if you must, but there are a lot of really good ideas here. Since this is a typology forum, though, I'll post the caveat that I'm not sure how realistic it is for certain types to take the advice herein, even if they recognise the advice as good.
The Picture of Dorian Gray, by Oscar Wilde - As a parable, it's a little heavy-handed, though the metaphor is striking and easy to understand, and the moral is a positive one. Wilde's prose is wonderfully clever, and his characters are superb. Lord Henry is one of my
favourite characters from any work of fiction.
Republic, by Plato - Without any doubt, the most brilliant piece of literature in human history. Anyone with the most meager interest in politics and/or human nature should read this. Take your fucking time, though -- really
absorb what the author is teaching you, and be prepared to wade through a lot of metaphor.
Brave New World, by Aldous Huxley - Scarier and more prophetic than
1984. Permit me to quote the foreword of Neil Postman's
Amusing Ourselves To Death: Public Discourse In The Age Of Show Business.
We were keeping our eye on 1984. When the year came and the prophecy didn't, thoughtful Americans sang softly in praise of themselves. The roots of liberal democracy had held. Wherever else the terror had happened, we, at least, had not been visited by Orwellian nightmares.
But we had forgotten that alongside Orwell's dark vision, there was another -- slightly older, slightly less well known, equally chilling: Aldous Huxley's Brave New World. Contrary to common belief even among the educated, Huxley and Orwell did not prophesy the same thing. Orwell warns that we will be overcome by an externally imposed oppression. But in Huxley's vision, no Big Brother is required to deprive people of their autonomy, maturity and history. As he saw it, people will come to love their oppression, to adore the technologies that undo their capacities to think.
What Orwell feared were those who would ban books. What Huxley feared was that there would be no reason to ban a book, for there would be no one who wanted to read one. Orwell feared those who would deprive us of information. Huxley feared those who would give us so much that we would be reduced to passivity and egoism. Orwell feared that the truth would be concealed from us. Huxley feared the truth would be drowned in a sea of irrelevance. Orwell feared we would become a captive culture. Huxley feared we would become a trivial culture, preocuppied with some equivalent of the feelies, the orgy porgy, and the centrifugal bumblepuppy. As Huxley remarked in Brave New World Revisited, the civil libertarians and rationalists who are ever on the alert to oppose tyranny 'failed to take into account man's almost infinite appetite for distractions.' In 1984, Huxley added, people are controlled by inflicting pain. In Brave New World, they are controlled by inflicting pleasure. In short, Orwell feared what we hate will ruin us. Huxley feared that what we love will ruin us.
This book is about the possibility that Huxley, not Orwell, was right.
Nothing is more important than making sure we understand who is really in control and what is really happening as a consequence.