“Bird Cloud” is the name Annie Proulx gave to 640 acres of Wyoming wetlands and prairie and four-hundred-foot cliffs plunging down to the North Platte River. On the day she first visited, a cloud in the shape of a bird hung in the evening sky. Proulx also saw pelicans, bald eagles, golden eagles, great blue herons, ravens, scores of bluebirds, harriers, kestrels, elk, deer and a dozen antelope. She fell in love with the land, then owned by the Nature Conservancy, and she knew what she wanted to build on it—a house in harmony with her work, her appetites and her character, a library surrounded by bedrooms and a kitchen. <P>Proulx's first work of nonfiction in more than twenty years, <I>Bird Cloud </I>is the story of designing and constructing that house—with its solar panels, Japanese soak tub, concrete floor and elk horn handles on kitchen cabinets. It is also an enthralling natural history and archaeology of the region—inhabited for millennia by Ute, Arapaho and Shoshone Indians— and a family history, going back to nineteenth-century Mississippi riverboat captains and Canadian settlers. <P>Proulx, a writer with extraordinary powers of observation and compassion, here turns her lens on herself. We understand how she came to be living in a house surrounded by wilderness, with shelves for thousands of books and long worktables on which to heap manuscripts, research materials and maps, and how she came to be one of the great American writers of her time. <I>Bird Cloud </I>is magnificent.