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...

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