Gödel, Escher, Bach has introduced new fields of thought to a generation of self-directed learners. A Nature review called it "an entire humanistic education between the covers of a single book". It's become a fixture in geek culture, even bleeding into popular culture once in a while.
It's a book that encourages you to participate in it. To fully experience it, you don't just read it, you do it by doing the math, listening to the music, participating in the culture surrounding it, and discussing the ideas you come across with other people.