That's McArdle's verdict:
Amazon reports that sales of e-books have finally surpassed sales of hardcovers. That's a pretty momentous development. I think it not only means that e-books are entering the mass adoption phase, but also that the price-discrimination model that publishers have used for decades may be on its way out. There's no significant benefit to buying most disposable mass-market books in hardcover; people do it because they don't want to wait for the paperback. In theory, they should be willing to pay extra to get a "new release" rather than wait a year, but in practice, people are surprisingly resistant...