Zen and the Art of Motorcycle Maintenance: An Inquiry Into Values by Robert M. Pirsig - GoodReads calls it 'one of the most important and influential books written in the past half-century.' Here is my favourite one of the 6,662 Reviews (by Richard):
There are three threads weaving through this book (none of which, as is pointed out, has much to do with either eastern philosophy or with motorcycle maintenance.)
The first is a straightforward narration by a man riding across the country with his young son and two friends (a married couple). This evocative travelogue is by far the most enjoyable aspect of the novel.
The second element is a sort of mystery as that man struggles with his memory; it's gradually revealed that he's on the road both to escape his past and to attempt to remember it.
The last thread is where the book just falls apart. Through the narrator's dialogue with himself, Pirsig puts forward his ludicrous "philosophy of quality," which essentially holds that "quality," whatever that might be, is somehow the fundamental reality of the universe. If that sounds like nonsense then you understand it perfectly.
When we find out why the narrator had lost his memory in the first place, the answers don't live up to any expectations we might have been unfortunate enough to have developed.