Released last week, J. Courtney Sullivan’s Saints for All Occasions is a family saga about two Irish sisters who set off for Boston in 1957. One gets married and has a family; the other ends up in a convent. Sullivan’s fourth novel is getting excellent reviews: “The Year’s Best Book About Families,” The Washington Post declared. The book opens in 2009 at a funeral and then untangles a half-century of family drama and Boston drama. The Boston-bred author comes to Westerly for a reading and conversation with Jill Santopolo.