In the course of their interviews Dalton Trumbo told Bruce Cook, who was too ""embarrassed"" to ask, that he joined the Communist Party casually in 1943 and drifted away, unaltered (""I changed no beliefs"") in 1948, then rejoined briefly in the mid-1950s--which is just what you might have learned from the New York Times Trumbo obituary. Cook's only equipment for writing a life of Trumbo, it appears, was a tape recorder, travel money, and admiration; he blithely presents as the results of his researches what is already on the public record (in Trumbo's own Additional Dialogue, for one) and, save for filling in details and soliciting more opinions, lets it stand unexamined. For him as for Trumbo (who knew better), communism is--in Dwight Macdonald's memorable phrase--no more consequential than the common cold; and Stalinism is nonexistent. The two areas he pokes around in are Trumbo's early life in Grand Junction, Colorado, where his father failed ignominiously, and his wild pursuit of his knockout wife Cleo. The first elicits what may be the book's only insight, credited to Karen Horney, that Trumbo's obsession with material success represented an urge for ""vindictive triumph."" An idealistic firebrand from high school days, Trumbo was radicalized, according to Cook, by eight years work at the Davis Perfection Bakery and exposure to the surrounding ""crummy"" environment. Not that ""social determinism"" defines him precisely; no, what is most ""remarkable"" about Trumbo, Cook concludes, is the way he himself shaped his time. A psychologically and politically gauche contribution to blacklist hagiography.