Motorcycle road trips have been a common vehicle for stories about the pursuit of freedom and wisdom. 1974’s Zen and the Art of Motorcycle Maintenance follows suit. Based on actual events in Robert Pirsig’s life (though he takes more than a few creative liberties), the book propels the narrator, Pirsig’s alter-ego Phaedrus, and the narrator’s son through a trip from Minnesota to California, expounding on some of philosophy’s time-old questions, with his motorcycle serving as metaphor for discussions on form and function, the romantic view and the classical view. The book mainly centers on the search for quality — what it is and how to define it. But far from reading like a dry philosophy textbook, Pirsig’s work weaves these thoughts into a compelling adventure. The book has sold 5 million copies and inspired several “Pirsig Pilgrims,” devotees that retrace the author’s route in search of similar stimulation.