I read “Zen and the Art of Motorcycle Maintenance” when I was in my 20’s. I read it again in my 30’s. Another time in my 40’s. Another time in my 50’s. I read it again in my 60’s. I never read the same book twice. I guess it’s like going to the River. You can never go to the same river twice. My son, aged 23, now has my highlighted and scribble-in-the-margins copy in his library.