Answer:
Actually, the person who answered before me is completely and utterly wrong. Stephenie Meyer, actually, has sold about 100 million copies now. But just barely. JK Rowling has sold over 450 million, if not more, and now she's allowed her series to be an e-book. So she'll sell even more. Twilight will probably never catch up to JK Rowling. Which is fine with me. JK Rowling can keep her spotlight :)