IN HIS FIRST NOVEL, Pride of the Bimbos , John Sayles did a brilliant tightrope-walking act. What can you say, after, about a barnstorming softball player who is a midget, wears a dress during working hours and has taken upon himself the duty of helping a boy through the rites of passage into American manhood? Somehow, Sayles said it, juggling his rather improbable symbols into patterns whose intricacy contributed a lot to their meaning.

Union Dues looks like a complete change of pace, a proletarian novel about ordinary, easily recorgnizable working-class people - West Virginia coal miners, Italian immigrants who work in a Boston meat-packing plant - and about kids, the kind of kids who gravitate to leftist communes and pass out throwaway leftlets on street corners, full of indignant rhetoric and grandiose plans for wiping out evil. No symbols, just the facts: the hard little details of what it is like operating the machinery that mines coal or makes sausages; the special kinds of discomfort encountered in a shaft full of coal dust, a production line, a refrigerated storage room, a desolate, snow-sodden street corner in Cambridge. What a book like this needs, and what you notice with special enjoyment on your first reading, is sharpness of eye and ear, plus the ability to present sympathetic characters engaged in activities that absorb your attention.

The central character is Hobie McNatt, nearing 18 and finishing his last season on the football team in a West Virginia coal-mining town, where he is the best runner folks in those parts have ever seen. On the eve of the last big game of the season, Hobie runs away from home for no clearly defined reason. (In a coal-mining town, where your future is spread out before you in the men who sit around coughing up black phlegm, you don't need to define reasons very carefully.) Hobie goes off to Boston, hoping to find his brother who left home after coming back from Vietnam. When Hobie's widowed father, Hunter, finds the boy gone, he packs up and goes after him. They do not see one another again in the course of the book, and appear together only in flashbacks.But there is a parallelism in their experiences, as chronicled in alternating chapters.

An important aspect of the book is when all this happens. The story covers a few months in late 1968 and early 1969, one of the low ebbs in recent American history from several points of view. In the background of the story, two elections are taking place: Richard Nixon is becoming President of the United States and Tony Boyle is remaining president of the United Mine Workers. The dream of the early '60s is in its final convulsions - violent demonstrations that will ebb away, long after this story has ended, in the uneasy calm of the tranquilized '70s. Jock Yablonski and his family are murdered; Fred Hampton is killed in Chicago. Unless you are looking for it, you don't notice how cunningly all this is woven into the story's subtly stated thesis.

It is a shameful simplification to spell it out baldly when Sayles weaves it so intricately into his concrete details, but one of the novel's clear if unstated theses is that American workers are exploited, not only by the owners and managers of the mines and factories but by the unions and even the revolutionary movements that are supposedly dedicated to their interests.

As stated here, this is hardly a new or striking idea; as embodied in Sayles's story, it is a fresh, sharp-edged experience. Read the novel carefull for its thematic development, and you find total mobilization, even small atmospheric details and bits of apparently random dialogue subtly supporting its basic themes.

In terms of plot, this novel, like Pride of the Bimbos, seems loose-knit until it is finished and you can see the whole structure. In style, it is very closely woven, dense yet highly readable, with occasional virtuoso exercises, as in chapters 4 and 24. But Union Dues is ultimately not a thesis-novel or a symbolic novel or a series of exercises in style; it is realistic novel about how life is in the working class and around its fringes. It works superbly on this level, and can be read with great enjoyment just for its action and descriptions - for the feel of streets and buildings and human associations, the authentic ring of its dialogue in accents that range from West Virginia to South Boston. Sayles does his basic business of storytelling neatly before indulging in more literary or philosophical excursions.

One way to judge a novelist's talent is by observing how many disparate elements he can weave into his book without losing focus, how many things he can summon up and synergize into a unity. By this standard, Sayles has a very considerable talent indeed.