Gift ideas -- choicest new books for the holidays; An eagle's-eye view of the USA; The Extraordinary Landscape, by William Garnett. Boston: New York Graphic Society. 183 pp. $49.95.

William Garnett estimates that he has spent close to 7,000 hours alone in the air as a pilot and photographer. ''To fly in a small plane and see the variety of beauty the USA has to offer is a thrilling experience,'' he writes. This belief has prompted him to gather together some of his noteworthy aerial photographs here.

The book is aptly titled. There is nothing ordinary in the color photographs that fill its pages. Landscapes from Alaska to Florida are pictured, and each photograph is indexed at the back of the book. It is William Garnett's artistic eye and craftsmanship that make this book unique. In his introduction Ansel Adams gives the book high praise, and in this case it seems warranted.