The Golden Door is that California spa where, for a piddling $1000+ per week, you can diet and exercise in elegant surroundings with an attentive staff hovering nearby. This item, written by the spa's founder, allows you to forgo the steep entrance fee and pamper yourself at home via a regular balance of movement, relaxation, nutrition, and joy. Included are exercises for different circumstances (the office, poolside), remarks on attitude, menus and tasty recipes (calories indicated), and brief testimonials from satisfied customers like Calvin Klein, Barbara Howar, and an unidentified former Cabinet member. With headings like ""An Invitation to the Good Life"" and ""Enjoy . . . Enjoy,"" a manicured entry that should slip easily into all those Gucci bags.