Literary lion Jay McInerney just bought a two-bedroom beach cottage in Sag Harbor for $1.4 million, the full asking price, reports The Post’s Jennifer Gould Keil. The abode with a working fireplace is just 1,200 square feet, a far cry from the East End manse he shares with his heiress-socialite wife, Anne Hearst. McInerney says it will be part writer’s retreat and part children’s playhouse, adding, “The area is steeped in literary history. It’s a few doors up from E.L. Doctorow, across the street from Alice Mayhew and around the corner from where John Steinbeck lived and wrote ‘The Winter of our Discontent.’ “