THE NEW YORK TIMES BOOK OF SCIENCE LITERACY, edited by Richard Flaste (Times Books: $24.95; 318 pp.). The New York Times' Science Times pages are a great crossover feature--science deftly dished up for the lay reader. This collection includes pieces that appeared between January, 1987, and March, 1990--as much of a hedge as a book can make against dated material. The result is the equivalent of a big bag of your favorite junk food--say, M&Ms. Each piece is a treat, even if you have to go someplace else (to a book on a particular topic) to get sufficient nourishment. And once you try one, it's hard not to keep nibbling; most of us know so little about science that we're delighted at the palatable way it's served here. If there's an occasional stale peanut--and the health articles can seem a little old--surely the next revelation will be fresher.