ANCESTRAL TRUTHS by Sara Maitland (Henry Holt: 22.50; 295 pp.). Although Sara Maitland has made a mark in her native Britain, in this country she is at present little known. "Ancestral Truths," one hopes, will change all that: This is truly accomplished and thoroughly literate storytelling, accessible yet intricate, comical yet contemplative, shrewd yet deeply empathetic. Clare Kerslake, a photographer, has returned to Scotland for the annual family vacation at her uncle's estate, and she brings with her a secret, unknown even to her: how she lost her right hand, and her lover his life, on Zimbabwe's highest mountain, Nyangani. That mystery is a minor one in this book, however, for Maitland's concerns are more profound: why people become what they become, do what they do, fear what they fear. Clare gradually regains her memory in the course of this summer sojourn, and her account of the fatal hike at the end of the book is mesmerizing, but it's Maitland's ability to capture the complexity of family relations that makes "Ancestral Truths" so compelling. All seven of the Kerslake children have their moments in the sun, and each seems essential to the family pattern: Joseph the dutiful eldest, Tom the trouble-free joker, Ceci the Carmelite nun, Ben the soon-to-be-defrocked gay priest, Anni the scientist, Felicity the pressured mother of a 5-year-old who cannot hear. Early on one wonders whether "Ancestral Truths" will fall into melodrama, given that the novel begins with Clare's accident and acquisition of a newfangled prosthetic hand, but Maitland's tone and language is in fact unerring. "Ancestral Truths" at first seems to be about loss, but ultimately it's about the need for risk and the inevitability of change.