A neither-nor book. Roberts, who would rightly end discrimination against fat people, tries to combine her personal story as a compulsive eater with a political directive. The result is hard to stomach. Roberts (sister of actor Tony Roberts) lives in London where she is something of a personality. Several years ago she made her debut in a small theater production concerned with compulsive eating, and the show garnered some attention. For a time she also hosted a TV talk show, ""Large as Life."" The book, then, is a natural extension of those public activities on behalf of herself and other oversized citizens. Unfortunately, despite a lively writing style, Roberts hasn't much of a story to tell. We are subjected to the mealtimes of her childhood, and to her adolscent passion for leftovers and Mars Bars. It's all given such serious treatment that the effect is comic. At times, reading Roberts is like wading through a confession magazine where only trivialities are exposed--""My Secret Life on the Searsdale Diet."" She finds salvation and a new way of life once she accepts that she is acceptable, at least to herself, in a size 22 or larger. A happy ending, indeed. But why should we care? Once Roberts' personal story is told, the book dribbles off into beauty and fitness. Again, her approach is too personal to be generally beneficial to large women. But overall, the book is an indulgence: Roberts is a public personality who thinks she has a story to tell.