That's similar to how I see it. My niece recently turned 16 and in a recent conversation I discovered she's into fantasy but hasn't heard of the Discworld novels. I looked up which book is commonly considered the best intro to the series (Small Gods) and bought her that. It might spark a real interest, or it might turn out that Discworld is too dated and unappealing to teenagers these days, but that bit of thought makes the odds better than random.