All those nostalgic for an unsullied New England have a friend in David Yeadon, who resolutely bypasses ski resorts, historic restorations, craft centers, and other tourist spots. His target is the leisurely motorist with a penchant for exploring out-of-the-way places (and no objection to getting lost). Connecticut offers, for example, the Cornwall region where dusty roads wind through deep forests--one, the Cathedral Pines, an accessible virgin stand. Rhode Island has the Great Swamp, site of the 1675 massacre of two thousand Narragansetts. Off the Massachusetts coast is Cuttyhunk Island, ""a place to enjoy your own company"" because there's virtually nothing else to do. But highly developed southern New England has relatively few ""hidden comers"" compared with New Hampshire and Vermont, in particular their northern parts. Anyone faced with ""a dismal day in St. Johnsbury"" will welcome news of the onetime ""Republic of Indian Stream"" nearby along the Canadian border, while the growing band of industrial historians will head for the Connecticut River milltowns of Claremont and Bellows Falls. In Maine, stretches of coast, Monhegan Island, and the hard-bitten potato country repay attention. With 150 sketches by the author, equally an invitation and a preview.