The classical definition of a Young Adult novel is any in which the protagonist is of high school age. So, while some may disagree, technically, Treasure Island and Lord of the Flies are YA novels. Also, YA novels are traditionally aimed at a 15 to 21-year-old audience (not early teens as some like to argue). Well, check out this latest item from Kirkus Reviews:
What rational adult willingly revisits adolescence? A lot of us, if a study released by Bowker, a prominent provider of data about books, is any indication—last September, Bowker revealed that 55% of people who read young adult books are over 18 (with the largest segment of those adults aged 30-44!). Young adult books have so captured the public’s enthusiasm that the publishing industry has concocted a new term for books meant for teens that aren’t actually read by teens: “new adult” books. Whatever they’re called, the genre has blossomed so creatively that being a responsible adult caught reading a novel meant for teens is no longer something to think twice about.