Precocious twelve-year-olds

Julia: This is so goofy. Gödel, Escher, Bach is listed as a Young Adult book in the library system.
Jeff: I think it is a young adult book.
Julia: Young adult books are for twelve-year-olds. Like Sweet Valley High.
Jeff: Most of the people I know who read it were teenagers at the time.
Julia: But that's true of Dune, and that's not a young adult book. Look - (flipping to a passage.) "We now 'squeeze' this sentence of English (the metalanguage) into the formal notation (the object language): <P⊃~~P>. This, our first theorem of the Propositional Calculus, should reveal to you the intended interpretation of the symbol '<⊃>'."
Jeff: Okay, you're right.