No doubt Mary Frances Kennedy (known as MFK) Fisher, now 82, is as vibrant, witty, and elegantly sensual a writer and person as her countless admirers delight in reporting. No doubt the world is richer for the recent reprinting of her old books and maybe even for the appearance of her newer ones. But do we now need whole books from others just attesting to her charms? ``It's hard to write about writers who write about themselves because they've already set down everything they want you to know,'' Ferrary (coauthor, Season to Taste, 1988, etc.) acknowledges here. Her solution is to eschew straight biography for appreciative memoir: She appreciates Fisher's ``high sense of life, her wired sensitivity...her radiating wit and style...her intensity,'' and much more of the same. And in prose that is often graceful and amusing if sometimes sticky-cute, she remembers 12 years of congenial visits and ``chatting-up times,'' with Ferrary agonizing over what gift of food to take this paragon of gastronomy and Fisher always coming through with just the right lunch dish and sparkling presence. Though Ferrary traveled f rom California to Radcliffe to study Fisher's papers in the Schlesinger Library, she is too good a friend to probe into her subject's private or inner life. The three husbands are barely identified and, of Fisher's lifelong devotion to her father, whom she called by his first name Rex, Ferrary says coyly, ``But I am a friend...I do not talk about Oedipus and Rex in the same sentence, as if I'm so smart.'' Instead, ``when I am with her we are laughing, we are wondering, we are twirling around.'' Privileged glimpses, then, for fellow worshippers.