Amazon Seeks E-Book Concessions from Publishers has threatened to stop directly selling the books of some publishers online unless they agree to a detailed list of concessions regarding the sale of electronic books, according to two industry executives with direct knowledge of the discussions. The hardball approach comes less than two months after Amazon shocked the publishing world by removing the “buy” buttons from its site for thousands of printed books from Macmillan, one of the country’s six largest publishers, in a dispute over e-book pricing.