An anniversary gift of bedtime ear plugs is a sign that something is missing in a long marriage. Carol, played by Mary Steenburgen, feels the sensual emptiness of her marriage more acutely after she and her book club pals - played by Jane Fonda, Candice Bergen and Diane Keaton - read the international best seller "Fifty Shades of Grey.""It's gotten me into a tizzy," Carol tells her friends in the romantic comedy film "Book Club," which opens May 18 in theaters nationwide.