It's Harry Potter.
Between the massive mainstream success of both
the books and movies, it's the obvious choice. People who don't even read were devouring the books within days and going to massive release parties. Every release was a genuine cultural event. It captured virtually EVERY demographic. I think people have started to forget exactly how massive Harry Potter fever was. Hogwarts, Dumbledore, etc, make a reference to them in any social situation and guaranteed at least somebody knows what you're talking about.