How opening up books increases sales

I missed this Wired magazine interview of Jeff Bezos earlier this month, but it's worth pointing to, especially this snippet:

[Wired] You launched Search Inside the Book about a year ago. What have been the main effects?

[JB] If you went into a physical bookstore, and all the books were shrink-wrapped shut, would you sell more that way? Probably not. But for the first eight years, that's what Amazon.com was. Now there are hundreds of thousands of books [that can be full-text searched]. Sales of those books are up 9 percent relative to others. We wondered about things like cookbooks and reference titles - would people just take the snippet they need and not buy the book? In fact, by letting people search inside, sales of these types of books have gone up more than average.

Slashdotters weigh in, too.