In the preface to “A Christmas Carol,” Charles Dickens wrote that he endeavored with his “ghostly little book” not to put his “readers out of humor,” but rather “haunt their houses pleasantly.” One hundred seventy-four years later, generations of readers and theatergoers are still spellbound by Dickens’ “ghost of an idea.” Footlights Theatre keeps his message of social change shining brightly, chasing away the holiday bah humbugs with an adaptation by executive artistic director Michael J.