This is because of an ongoing feud that Amazon is having with Hachette. For those unfamiliar, Hachette is one of the top five book publishers, which also includes HarperCollins, Macmillan Publishers, Penguin Random House, and Simon and Schuster. Amazon and Hachette are currently negotiating a deal with one another, but in the meantime it looks like Amazon is making life difficult for the publisher, its writers, and its customers.
This is done by either delaying the shipments of Hachette-published books, pricier physical books, as well as recommendations for alternative titles in their Amazon listings, which would essentially drive customers away from Hachette-published books to another company. We’re not sure if the latter strategy works since not two books are alike.
It seems that Amazon is doing this to frustrate writers who make royalties of books sold, and if no books are sold, then they don’t get paid. Frustrated writers will then go to their publishers and pressure them to give in to Amazon’s demands. There is a good chance that Amazon will come up on top, but in the meantime if you were hoping to get the latest title from the Harry Potter series by J.K. Rowling, you’ll probably want to look elsewhere.