Diana Athill... on two types of readers

I couldn't find an apt place to include this quotation in my review of Diana Athill's Stet yesterday, but it's so wonderful a quotation that I had to put it up somewhere:

People who buy books, not counting useful how-to-do-it books, are of two kinds. There are those who buy because they love books and what they can get from them, and those to whom books are one form of entertainment among several. The first group, which is by far the smaller, will go on reading, if not for ever, then for as long as one can foresee. The second group has to be courted. It is the second which makes the best-seller, impelled thereto by the buzz that a particular book is really something special; and it also makes publishers’ headaches, because it has become more and more resistant to courting.

How simply this clears up my confusion over 'Why did that become a bestseller?' - or even the concept of the bestseller at all.  The second group, as she details later in Stet, would just as happily turn to music or television or cinema for their entertainment.  Those of us in the first group (though of course we might well enjoy music, television, and cinema) cannot imagine a substitute for books.  Nothing comes close.