Here are some quotes from the article:

Amazon’s third-party sellers have to offer new books, not used ones, but in many cases they don’t seem to have bought their books from publishers. No one is quite sure where their books come from, including, it seems, Amazon itself. -- Some of the comments in this thread link to pictures of counterfeit books.

If the Buy Box winner for a book is out of stock, it will look to most customers as though the book is out of stock everywhere. -- This would cost the author a sale. Many shoppers don't realize that the Buy Box is only one merchant out of many.

This policy is part of Amazon’s ongoing, years-long quest to drive down the price of books. -- See the App Store for the endgame of race-to-the-bottom prices.

How would an offer which is out of stock win the buy box? I'm pretty sure that if there's at least one seller with stock, that the buy box would show one of them.

Did you read the article? This was mentioned and multiple tweets were quoted.

Yes, I did. And followed the links in the Tweets. The article suggests that it's possible that the buy box winner is out of stock, whilst at least one seller (Amazon or a third party seller, e.g. the publisher) is in stock. The tweets don't assert that. The links and screenshots referred to by the tweets also demonstrate no such thing.

Specifically, regarding the tweets:

- One of the links is to an Amazon page. The winner of the buy box when I open the page is 'In stock'

- The other link is to a HuffPo article, which contains some screenshots. The screenshots include buy boxes, but none of the screenshots show a buy box that's been won by an out-of-stock seller.

Piracy/counterfeiting is a real concern