An expert, up-to-date guide to walks and hikes, most within an hour of two of New York City, including Hudson Highlands, Rockland County and Harriman Park, the West Hudson Hills and Shawangunks. The authors are past president and vice-president of the New York-New Jersey Trail Conference. With 51 maps, black-and-white photographs and an excellent at-a-glance overview.  (NYC90, $16.95)