I liked this age-ranging quote from Alan Garner:
Books are not shoes. They are not shirts. They have no sell-by, nor read-by dates. Their content is a unique creative interaction between text and reader. The evidence of my correspondence files going back nearly half a century show an age span of more than sixty years of people willing to engage and re-engage with the same titles. Whoever devised age banding knows how to sell detergents.