While it's true that most cook books are geared to four to six diners, it seems no great trick to double a recipe. Still Rubenstein does make a few useful suggestions about the logistics of cooking for large numbers--the optimal size of pots and pans and the savings which can be achieved by purchasing in quantity. The recipes, mainly old standards--Southern fried chicken, Wiener Schnitzel Holstein, baked stuffed striped bass--fortunately tend to eschew elaborate, manystep preparations. Even so, it's difficult to imagine the oven which will handily accommodate six 4-lb. ducklings at one time. Rubenstein is inclined to be spare with his seasonings--eggplant parmigiana with neither basil nor oregano seems somewhat bland. A convenience for large families, the book is for people who like good food but can do without truffles and foie gras.