In 1971, Frances Moore Lappe's Diet for a Small Planet introduced a vast American public to the idea that combining nonmeat foods can produce a ""complete protein"" meal; since then, countless vegetarian authors have come to realize that insuring adequate protein is not that formidable a task. Now comes seasoned vegetarian author and radio nutritionist Null, who agrees that ""knowledgeable vegetarians"" don't have to ""fret over exact food combining""--and who then justifies yet another book on vegetarian nutrition by announcing his breakthrough--a ""protein combination project"" that uses a computer to calculate what no one needs to know. But though computer analysis of amino acid content may well have value for nutrition research, it's just a gimmick here. And without it there is nothing new in Null's disorganized reiteration of vegetarian arguments (ecological, economical, ethical; his fuzzy discussion of vegetarian protein needs; or his retro vegetarian recipes, which mix Lappe's earnest additive approach (soy milk, brewers' yeast) with his own arbitrarily ""creative"" food combinations. (One simple dish, called ""bulgur coco-cado,"" dresses up the bulgur with avocado, asparagus, coconut and peanut-butter.) Though Null's nutrition counsel is perfectly safe and basically sound, and his wide audience guarantees that it will be lapped up, readers seeking precise enlightenment on vegetarian nutrition--and appealingly wholesome vegetarian recipes--will do better with the Robertson/Flinders/Ruppenthal's New Laurel's Kitchen (1986).