FRONTIER, text by Louis L'Amour. Photographs by David Muench. (Bantam, $29.95). This is a wonderfully appealing picture book, both in text and photos, the product of two talented lovers of the outdoors who have shamelessly, and with good cause, glorified the natural beauty of this country. The "Frontier" of the title is given its broadest definition, for as popular Western novelist Louis L'Amour points out, America's first frontier began on the Atlantic coastline. In 26 short, sharp, anecdotal essays, L'Amour evokes the pioneer experience of the country's many frontiers: the islands of Maine, the Louisiana bayous, the unforgiving deserts of the West and -- of all places the one he likes best -- the mountain "high country." This is a text to be read and co-enjoyed. The 140 photos by David Muench, the noted landscape photographer, are gorgeous, and none more so than a two-page vista at Cumberland Gap on Virginia's southwestern border, where a wispy puff of fog settles lightly over the forested ridges.

EYE ON AMERICA, photographs by Michael Ruetz. Introduction by William Least Heat Moon. (Little, Brown, $50). Inevitably, the foreign visitor is asked, "And what do you think about our country?" Michael Ruetz's answer, as seen in his collection of 84 cityscapes and landscapes, is highly favorable. A German photojournalist with a number of books to his credit, he spent two years exploring the United States, an odyssey in which, he says, he drove an average of 130 miles a day. Clearly he was impressed by the natural scenery, capturing, for example, the exquisite red-flamed beauty of dawn and dusk at Utah's Monument Valley. And he obviously welcomed what are still America's wide-open spaces. It is possible, he writes, "to find as much solitude in America as in the Antarctic."

DELAWARE: Small Wonder, photographs by Kevin Fleming. Text by Jane Vessels. Maps by Marley Amstutz. (State of Delaware and Harry N. Abrams, $45). This is the State of Delaware's unabashed (and full-color) picturebook tribute to itself. But, as the photos illustrate, Delaware has much to praise. Each of the state's three counties is profiled -- the people, the countryside, the cities and villages, the industry. A fine selection of photos is accompanied by full and informative captions. Thousands of Washington vacationers who know only Delaware's summer beaches might be intrigued by this book to discover the state's historic cities and scenic countryside. And for what appears to be an official book, it displays a certain sense of humor. On page 49 is an evening view of an oil refinery's flaming stacks. In the forefront, a lighted sign describes the all-too-obvious: "Scenic Road Ends."

TWO OZARK RIVERS: The Current and the Jacks Fork, photographs by Oliver Schuchard. Text by Steve Kohler. (University of Missouri Press, $24.95). In their combined lengths, the two rivers, the Current and the Jacks Fork, flow only 130 miles through the Missouri Ozarks, the Jacks Fork emptying into the Current, which itself flows into the Black River. But these two Ozark rivers have a significance beyond their size. In 1964, Congress established them as the nation's first federally protected scenic rivers -- the Ozark National Scenic Riverways -- a wilderness refuge of rocky cliffs, rumbling waterfalls, quiet pools, bubbling fresh springs and the now-decaying barns and mills along fern-lined banks. The book is a beautiful photographic ramble down the river valleys, designed, as Oliver Schuchard writes, to make more Americans aware of them. For, he argues, the best defense against encroaching development is strong public appreciation of their value.