Bird Cloud is the name Proulx gave to 640 acres of Wyoming wetlands and prairie and 400-foot cliffs plunging down to the North Platte River. Her first work of nonfiction in more than 20 years, "Bird Cloud" 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. 256 pp. 100,000 print.