The vegetable fare in America has been noted for its dullness and limitations,"" declares Kay Shaw Nelson, who along with the Romagnolis, is doing her part to remedy this gustatory dereliction. The Romagnolis add fish, pasta, and risotto to their traditional zucchini, eggplant, artichoke, and mushroom dishes; Nelson ranges into Persian, Oriental, and Latin American specialities, serving up such things as corn-stuffed Mexican pimentos, Hong Kong spinach-mushroom soup, and curried lentils from Pakistan. There is absolutely nothing penitential about the Romagnolis cucina di magro (literally, the spare meals served during Lent and on fast days) since such delicacies as truffles, olive oil, fresh basil, and walnuts combine with (preferably) homemade pastas--which they swear is easy. Not to mention magnificently sauced squid, trout, and tuna dishes or Italian versions of onion or asparagus soup. Nelson's recipes tend to be botherless and eclectic--she's no purist and adapts freely. The Romagnolis, inheritors of a subtly accented national cuisine with many regional variations, are much more exacting and perfectionist. Both books belong on the shelf if you're trying to cut down the family's meat intake.