Welcome help for those who care enough to cook for friends with dietary problems. The special nutritional needs of such dinner or weekend guests can be daunting; but Eisenberg has managed to provide a week's fare each for calorie-counters, the ""cholesterol-cautious,"" sugar-avoiders, low-salt dieters, vegetarians, the ""Pritikin proselytes,"" kosher guests, those on bland or milk-free diets, and assorted others. After some tips for successful entertaining (check in advance for specific needs, allow for self-service, serve trimmings on the side), each chapter addresses a single problem--first explaining the diet (why it's needed, why it works), then setting forth the recipes. The latter are suitably festive (curried pea and avocado soup, cold pasta primavera) and commendably free of ersatz substitutes for real foods. (Eisenberg does rely strongly on frozen apple juice concentrate.) If the problem is a daily one and disease-related, Goodman and Morse's Just What the Doctor Ordered (below) is the source to look to; to feed the occasional visitor, and cope with a wide range of peculiar diets, try Eisenberg.