Writing a history book about four centuries of Long Island’s East End is rather like squeezing 12 adult humans into the trunk of a Maserati — it is going to be a tight fit. Marilyn E. Weigold, a professor who teaches at Pace University in the department of economics, history, and political science, has chosen to let the blue waters of Peconic Bay form the matrix for an engrossing collage of folklore and facts that tells an abbreviated but well-curated episodic history of Long Island’s eastern forks.