From Amazon, a Change That Hurts Authors - The New York Times

So when you, the customer, hit that main buy button, you should always expect to get a brand-new book, right?

Not necessarily.

To explain why, we have to take a journey into the underbelly of the book market. Have you ever asked yourself, when shopping for books on Amazon, how third-party sellers can be offering dozens of "new" books at prices way below even the discounted Amazon price? The reason is that such books could have been bought in bulk by a handful of giant online third-party sellers to be re-sold through Amazon as "new" books, when some are not.