Our guest on ST is Margot Livesey, the Scottish-born, Boston-based writer whose work has earned a Guggenheim Fellowship, a National Endowment for the Arts Fellowship, the PEN New England Award, and the Massachusetts Book Award. She tells us about two of her books, "The Hidden Machinery: Essays on Writing" and "Mercury: A Novel." Of the latter, the New York Times noted: "Livesey knows her way around human desire and disappointment. Like the recent blockbusters 'Gone Girl' and 'Fates and Furies,'