Writer Charles Long has a well-earned reputation as one of North America's self-sufficiency experts. More than 20 years ago, he and his wife, Elizabeth, fled city life and conventional employment for the country, and have flourished there ever since. Now back by popular demand Long's The Stonebuilder's Primer is a highly readable account of the couple's successful effort to build ''a house that will outlast anything made of wood.''Developing a compromise method of stone construction that is both simpler and truer to the stonemason's art than the popular slipform method, the Longs built an aesthetically satisfying home of stone on a limited budget and no previous construction experience. In this classic how-to book, the author describes the complete building process in clear, easy-to-follow steps and, in so doing, dispels the myth of difficulty that surrounds stone construction.