An occasionally uneven but generally satisfactory book of recipes for those who watch everything--calories, cholesterol, and fiber intake. The authors have worked it out so that 4 oz. portions of their carefully planned meals will assure daily cholesterol levels of 175 to 225 milligrams--well below what most Americans are getting. There are some necessary substitutions: Egg Beaters, Morningstar sausage patties (made of soy beans), Bacos, and low-fat margarine. But the fare is pleasantly varied and the low-calorie chicken and fish dishes are good enough for company. If you must sin there are also directions for baking thickcrust pizza and for lox-and-bagel noshes (substitute ricotta for the cream cheese). Useful--and with due regard for the limits of human will power.