THE GRIZZLY BEAR By Thomas McNamee. With drawings by Gordon Allen. 308 pp. New York: Alfred A. Knopf. $18.95.

The grizzly bear is the subject of a controversy among scientists, park managers and lay citizens that, over 40 years, has produced a blizzard of scientific papers and several shelves of books. What has been needed, for some time now, is a balanced, comprehensible work encompassing the results of the research and assessing the needs of the bears and of the people who live within their range. In ''The Grizzly Bear,'' his first book, Thomas McNamee has given us that work.

Events since Mr. McNamee completed his manuscript only confirm the urgency of his book. The summer of 1984 was a bad one in the northern Rockies - five persons were mauled by grizzlies in Yellowstone and Glacier National Parks. On July 30, a Yellowstone camper was dragged from her tent and killed by a grizzly that apparently devoured all but 12 pounds of her body.

A year later, the Montana Department of Fish, Wildlife and Parks has begun soliciting public comment for a preliminary draft of an environmental-impact statement on the future of the great bears. Some researchers have sought to explain the terror in terms of addiction. One widely publicized theory supposes that bears used in studies, repeatedly tranquilized with phencyclidine hydrochloride (also known as PCP and angel dust), may have become blindly aggressive, in the manner of humans who sometimes become violent under the influence of that drug. Another group believes that Yellowstone bears have become addicted to garbage and that the decision in the late 1960's to close the dumps set grizzlies on the course of mugging passers-by for a quick fix. This group has suggested opening a few small, remote dumps to put the bears on a program of phased withdrawal. A group of local hunters has proposed a national-park grizzly hunt to re-establish the bears' fear of humans, while others say that the breeding pool is already too small and that the bear is gravely threatened.