One of my fondest memories of the annual Manila International Book Fair is when National Bookstore and Goodwill Bookstore (the only two big bookstores present at the time) entered a price war on one of the Harry Potter books. If I remember correctly, the fifth book had just come out a month or two before and as expected, both bookstores overstocked on it. Then comes in the book fair and they declare Harry Potter books on sale. Of course while it began with the usual 20% discount, by the end of the book fair, each bookstore was selling it at 40% off.
I bring this up because the seventh Harry Potter book is about to be released, and a few months way from the book fair. I think it's a safe call to say bookstores will again overstock Harry Potter. The question is what solutions they'll come up to solve this problem (whether it'll go as low as 40% off again looms in my mind but I honestly doubt it). There's also the fact that nearly every bookstore and reading organization has a Harry Potter promo of some sort so it's interesting to see how this all plays out.