Harry Potter, for all of you who've been asleep or vacationing on some far planet, is the biggest thing to have hit the publishing scene since, well, since I don't know when. He's huge-I mean, huge for a rather thin 11-year-old English kid with unruly hair and specs. The three books so far published have earned his creator, J.K. Rowling, an unassuming young woman, an almost mythical amount of money and have sold in well-nigh legendary quantities. They've shot her young hero into the limelight-the cover of Time, for example, and you can't get a limier light than that.