Twain Marketing

I recently saw this on a writing newsletter I subscribe to and thought I'd share it here since it goes along with my last two entries on "Marketing." Hmm. I wonder if this is what JK Rowling did, too.
"I conceive that the right way to write a story for boys is to write so that it will not only interest boys but strongly interest any man who has ever been a boy. That immensely enlarges the audience."~ Mark Twain, Letter to Fred J. Hall, 8/10/1892