Zen and the Art of Motorcycle Maintenance is a book with many virtues and many flaws, which definitely makes it a must-read. I initially read this book when I was sixteen and I identified with it strongly then. and I re-read it again to see how it related to the significant progress of my own life (I'm 28 as I write this).
The flaws in the book include the lack of rigour, the sometimes rambling and incoherent prose, and, in general, a lack of clarity in vision. This may sound harsh, but considering other philosophical works of this nature (among the ones that have influenced me, the best ever has been G"odel, Escher, Bach: An Eternal Golden Braid by Douglas Hofstadter), this particular one pales in comparison. Still there are many virtues and I'll primarily focus on them here, keeping in mind that you might have to work a bit to get through this book (everyone else I've spoken to about it has not managed to finish it).
A surface-level appeal of this book to me when I was younger, and even now, is that it goes into some detail about maintaining a motorcycle. As someone who owned a motorcycle and spent time tinkering with it, reading about engine seizures and rich cylinders was almost sentimental for me. Pirsig uses the notion of motorcycle maintenance to illustrate the core idea that I got out of Zen and the Art of Motorcycle Maintenance, which is about reconciling classical and romantic modes of thinking. This reconciliation is something I've managed to do in my life and enjoy immensely. However, in this respect, G"odel, Escher, Bach has been a bigger influence (Hofstadter talks about the reconciliation of reductionism and wholism). The reason is that the latter is far more rigourous in its treatment, combining the mathematics, the sciences, philosophy, and the arts in a coherent manner. Pirsig essentially neglects the mathematics and the sciences when he talks about the metaphysics of Quality. The Zen aspect of this reconciliation comes in accepting the fact that there are bound to be fundamental contradictions when that occurs (which, in the case of number theory, is predicted by G"odel's Incompleteness Theorem).
One of the most clever ideas in this work is the notion that even though the "purpose of [sic] scientific method is to select a single truth from among many hypothetical truths", "it is science itself that is leading mankind from a single absolute truths to multiple indeterminate ones". This is not platitude---the more we know, the space of the unknown becomes larger (it is not that we discover that it is larger, but that it actually becomes larger). This is like the theory of relativity which predicts that as we travel faster, the time taken is lesser (not just that we get someplace sooner). As a scientist, I completely agree, but that's the beauty of doing science (in a way, it's job security), and the reason wholistic approaches are essential (the expansion occurs only in the classical mode of thinking; as a romanticist, you can putatively view the entire Universe in one single clear thought).
Pirsig quotes Einstein (in page 115) as saying "Evolution has shown that at any given moment out of all conceivable constructions a single one has always proved itself superior to the rest," and using that as an argument to bolster the view that there are multiple indeterminate truths in science. While that statement about evolution is wrong, the statement about science isn't: in fact scientific theory in the 20th century itself points to such truths (from relativity and quantum mechanics to G"odel's Incompleteness theorem). Pirsig at times does come-off a bit as a techno-luddite. There is also strong new-age spiritual quality to this book that only burdens it. The conundrums Pirsig focuses can easily be dealt without resorting to fluff. Again, I refer to G"odel, Escher, Bach for a better treatment.
Pirsig makes a lot of excellent points throughout the book, which is the reason it is worth a read. For example, he comments that institutions serve their function and seek to subvert the individual to their own end. He illustrates this using academia as an example where students are taught to imitate and the idea of teaching involves thinking like the teacher. In my view, the only thing worth teaching is how to learn. This is something that can't be accomplished by grades, degrees, and generally by classroom teaching (where the pure motivation of wanting to learn can easily be corrupted by a desire to earn better grades or earning a degree), which is why I prefer the mentor-mentee relationship. There are some subjects where directed mentorship benefits (mathematics, for example), and this is more generally true when the subject of life itself is considered. However, freedom to learn and to question (something I've been raised with as far as back as I could remember) is arguably the most important condition to instill a passion for learning. In any event Pirsig's comments about institutions hold water much better when applied to governments and religions.
Another problem Pirsig points out is that over time, we've ignored our romantic side because the classical side has produced immediate gratification. As Pirsig also points out, this dichotomy, created by the Greeks, shouldn't have been created in the first place and leads to dissatisfaction. The solution of course, is to pay no attention to this dichotomy, which in my view is socially created, and ignore the notion of "right-brained" vs. "left-brained" talents. This is the dualism disease that Pirsig laments about.
The story itself has a degree of suspense thanks to the mysterious allusion to the schizophrenia that the narrator of the book has, fighting between an ideal and pragmatic self. The ending is particular interesting when the side that was in the background takes over.
Fundamentally, the whole book is about an inquiry into values and the notion of a contextual Quality which I won't get into except to say that in terms of a philosophy of life what matters most is being content (perhaps that's the same as "achieving" Quality). Ergo, if Pirsig's view is to tell us what Quality is, then he's guilty of the same things he accuses others of doing in the book. If his goal is to inspire Quality, then my above comments hold because his words have provoked me. In the latter regard, Pirsig at least points to a few reasons for discontentment and forlornness in current society and understanding them may help alleviate those conditions and improve one's self.