THE POLITICAL CURRENTS running beneath Hollywood's generally apolitical surface are easily apparent these days. Liberal acolyte Ed Asner is president of the Screen Actors Guild, and his SAG predecessor Ronald Reagan is president of the United States.

But the actors have nothing on the writers, and these days have nothing on those days--as far as political involvement goes. The screenwriters who came to Hollywood with the talkies easily established themselves as the town's premier pamphleteers, organizers and ideologues. Their union became the most contentious of Hollywood's guilds. And their ranks were the most deeply hit by the blacklist.

The Hollywood Writers' Wars chronicles the jousts-- intramural and otherwise--of Tinsel Town's politically active scribes from the creation of the Screen Writers Guild in 1933 to the beginning of the blacklist in 1947. "It was a great time to be prosperous, young, and progressive in the movie kingdom," write the authors. "You could live better than nine-tenths of the nation yet remain, through political activity, intimately connected to the pulse of humanity."

The era produced an enormous harvest of details for the daughter-mother team of Nancy Lynn Schwartz and Sheila Schwartz (the former did the research and wrote the first draft; the latter took over after her daughter's sudden death in 1978). Unfortunately, The Hollywood Writers' Wars is overwhelmed by its details.

The only organizing principle behind the book is chronology; subjects that span the entire era are scattered into fragments. Quotations from interviews are insufficiently edited for trivia. There are too many lists of names, yet occasionally people pop up without first names. When the Schwartzes do try to connect the details, their words are often banal or awkwardly phrased. The same subject is covered more gracefully and coherently in The Inquisition in Hollywood, by Larry Ceplair and Steven Englund.

Despite these obstacles to easy reading, The Hollywood Writers' Wars may be worth the effort for students of Hollywood or left-wing politics. In their discussion of Communist Party secrecy, for example, the Schwartzes offer the dubious generalization that "all young people yearn for secret societies," but they also relate how Ring Lardner Jr. "found himself in a situation at MGM where, on the phone, he would refer to Party meetings as 'the poker game.' Lardner also used to participate in a high-stakes poker game with the head of the MGM music department. He didn't like the idea of his poker playing becoming common knowledge, so on the phone he'd refer to the poker game as 'the meeting.' . . . Lardner spent his evenings going to poker games he called meetings and meetings he called poker games."

The Schwartzes conclude that the Hollywood Communists "got more from being in the Party, in terms of a social context, a sense of purpose, and intellectual stimulation than the Party actually got from them in terms of money and help in effecting a class revolution in this country." There is no evidence that communist doctrine was inserted insidiously into the movies by the Communist writers. However, as this was ostensibly the primary public concern that led to the blacklist, the Schwartzes should have devoted more space to showing how ludicrous such a charge was. They pay little attention to the movies themselves.

The Hollywood Writers' Wars does make clear that the Communists were effective soldiers in the common causes they shared with liberals. The most prominent was the anti-Nazi effort. Some of the more farsighted left-wingers--including Lardner and Dorothy Parker-- were to be tagged during World War II with the government's sublimely idiotic appellation "premature anti- fascist" and were consequently denied positions in which they could have actually helped fight the fascists. However, the Communists' record of prescience was severely marred by the Soviet-German non-aggression pact in 1939--a jolt that cast a considerable cloud over Hollywood's left-wing camaraderie.

Another awkward moment for the Communists was when the party forced critic Charles Glenn to recant his praise of Budd Schulberg's What Makes Sammy Run? The Schwartzes interviewed Glenn and Schulberg and also paid considerable attention to Schulberg's wife at the time, Jigee, whom they describe as the love goddess of the Hollywood Left. Fans of What Makes Sammy Run? will experience d,ejMa vu during those parts of The Hollywood Writers' Wars that cover the union activity around which Schulberg set his novel.

The Writers Guild is the most enduring legacy of the activist writers of the '30s. When the decade began, some producers kept goosing sticks with which to prod and humiliate their writers. They dunned the writers for Republican campaign funds, instituted arbitrary pay cuts, usurped film credits. The studios tried to crush or at least avoid the Guild, but the writers were persistent. At one Guild recruiting session, Lillian Hellman emerged from a t.ete-a-t.ete with an undecided male colleague and remarked that if she were to persuade the man to join the Guild, "somebody's got to pay for the abortion."

The Guild still hasn't achieved all that it wanted. But conditions have certainly improved. The vision of the "Screen Writers Marching Song," a 1934 ditty quoted by the Schwartzes, has more or less been fulfilled:

Drink! Drink! Drink! Drink! Write a master piece!

Till twenty thousand pages have been filled.

They'll all be thrown away

But the producers have to pay

To members of the Screen Writers Guild!