Whether the subject of leftovers--that extra brown sugar, that remaining quarterpint of cream--deserves an entire book or not, the recipes assembled by this team of veterans are good to have around. The selections are arranged alphabetically according to critical leftover ingredient (cheese, fresh herbs, mushroom stems), with tips on use and storage. The result is even more of a grab-bag than most cookbooks these days, and the writing is pure service-feature. Nonetheless, the material will be welcome to a great many homemakers, and the assorted offerings include such pleasures as buttermilk fudge, Rhode Island jonnycakes, bulgur-vegetable pilaf, and dried limas baked with white wine. Functional and agreeable.