Budiansky, a writer at U.S. News and World Report, may not provide as many ``insights into the true nature of the beast'' as he hopes, but he serves up fascinating historical, behavioral, and biological nuggets about our equine friends. Troubled that our understanding of Equus caballus is badly flawed, Budiansky (Nature's Keepers, 1995) endeavors to set the record straight, clearing the air of ``what millenniums of tradition, love, and wishful thinking have sometimes muddled,'' and telling the horses' story through the ``objective tools of science.'' He starts at the beginning of domestication, 6,000 years ago, with the Sredni Stog people. They, it is surmised, either clambered atop the horse or ate him; their bones are mixed together at archaeological digs in the Ukraine, marking the onset of a long, fruitful association. Horses and humans discovered what they had in common: an intuitive language of dominance and submission, an adaptation to grasslands, a social fabric built on subordination to authority and trust. Budiansky's portrait delves into mitochondrial DNA analysis, the mechanics of movement and eyesight and vocalization, but he's hesitant to guess at the ultimate meaning of this data. He is less edifying but far more entertaining when he occasionally hazards subjective rather than scientific information, as in his observation of the horse's ability to interpret subtle social cues shared with humans (dispelling notions of horses as mind readers) or when he simply throws out an idea he has concerning their fabled homing instinct. And he's incisive when describing the curious world of the stud book and the ambiguous effects of inbreeding. As a science journalist, Budiansky brings together a wealth of equine research; as the devoted horseman he is, he knows there is more than the objective interface, and that magic is a persistent part of the equation. (70 drawings and photos)