Dear Phil,
Duma Key is a fictional Island ... I have found a note from Chuck Ferril the longtime editor of Stephen King which you should find interesting
Duma Key : Where It All Began
A Note from Chuck Verrill, the Longtime Editor of Stephen King
In the spring of 2006 Stephen King told me he was working on a Florida story that was beginning to grow on him. "I'm thinking of calling it Duma Key ," he offered. I liked the sound of that--the title was like a drumbeat of dread. "You know how Lisey's Story is a story about marriage?" he said. "Sure," I answered. The novel hadn't yet been published, but I knew its story well: Lisey and Scott Landon--what a marriage that was. Then he dropped the other shoe: "I think Duma Key might be my story of divorce."
Pretty soon I received a slim package from a familiar address in Maine. Inside was a short story titled "Memory"--a story of divorce, all right, but set in Minnesota. By the end of the summer, when Tin House published "Memory," Stephen had completed a draft of Duma Key , and it became clear to me how "Memory" and its narrator, Edgar Freemantle, had moved from Minnesota to Florida, and how a story of divorce had turned into something more complex, more strange, and much more terrifying.