On March 1, Amazon enacted a policy change that allows third-party sellers to compete for the Buy Box for books in “new condition.”
When you go to a product page on Amazon, the ADD TO CART Buy Box is the default offer. Other used options fall below the Buy Box. Where books are concerned, the default Buy Box has always belonged to the publisher. When you buy a book, Amazon pays the publisher 45% of the list price. This means your purchase is supporting the entity that published the book, namely the publisher, and authors are making a profit (albeit small) every time you buy because the publisher is paying an author royalty for each sale.
Now Amazon is giving that priority spot to third-party sellers… [go to source for more]