Not only was it not, but the philosophical content it did have didn't seem particularly interesting — the long deliberations on quality felt like inconsequential hair-splitting that was unlikely to any revelations of value. Afterwards, I read the Wikipedia analysis on its philosophical themes [1] and felt that it's far too charitable in attributing significant insights to Pirsig compared to the literal contents of the book.
My guess is that the novel structure of weaving together a motorcycle trip with inner monologue and personal history combined with a dash of intellectualism was very compelling to a lot of people, and that's why it's taken such an outsized position in popular literature.
(I'd love to be proven wrong on this though, so by all means tell me what I missed.)
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[1] https://en.wikipedia.org/wiki/Zen_and_the_Art_of_Motorcycle_...