I clicked the link thinking it wasn't that. Because I know and love that book. For those that haven't read the sequel Lila, I highly recommend it also. It goes into what Quality actually is in enormous detail, how it works, the different types and levels. While ZAMM is typically concerned with relatively simple systems (like a motorbike) and how humans interact with them, Lila is more the biological, social, societal systems humans are a part of, anthropology/anthropologists trying to study them, and how those systems work, how each has its own Quality.. (long story!)
A few years ago I read Thoreau's A Week on the Concord and Merrimack Rivers (1849) and was immediately struck by, well, the form is exactly the same as Pirsig's books - nature/observation writing interspersed with slabs of philosophical/theoretical. Lila is even mostly set on a boat going down a river also. Thoreau probably does both styles better, but Pirsig has a focused theme - 'has something to say'. So if you like Pirsig, you'll love Thoreau's travel books.