I remember who lent me this book in HS, in what class, and the fact that I read the last page at his suggestion. That single page pushed me into a three to four year spiral of sci-fi reading that changed my life. perhaps not for the better or the worse, but changed I was. Mind-bending lit tends to attract we introspective, depressed nerds, but this book had such power that nothing else I read really struck me as hard (maybe Larry Niven's The Mote in God's Eye, but even that was a different fascination -- and I only read that one once). But Clarke introduced me to Niven and eventually I found myself buying stacks of used sci-fi.
I mean, what better compliment than "this book made me read more"? Only John Steinbeck can share that distinction in that point of my life.