Trouble in coal country during the Depression; Hardcastle, by John Yount. New York: Richard Marek Publishers. $10.95.

The hero of John Yount's new novel about the lives of Appalachian coal miners during the Great Depression can't quite see himself that way, though he's locally famous as the man who "once shot down a pair of deputy sheriffs," and is pestered for heroic tales by his grandchildren. This in a brief prologue and epilogue, each set in 1979, long after the events the main narrative describes.

That narrative begins, unheroically enough, in 1931 as William Music, heading home by boxcar from Chicago, is "captured" raiding gardens and henhouses for his dinner. He is befriended by captor Regus Bone, a mine guard at the Hardcastle Coal Company in Elkin, Ky., and Regus's affectionate mother, ella.

Music, too, becomes a mine guard, sworn to keep away "unionizers and Reds." He tells himself, "It's a depression and a man would be a fool to turn down three dollars a day." But it isn't long before Music sees things through the miners' eyes; he feels "guilty- . . . personally responsible," "more like a thief than a watchman." He falls in love with a young miner's widow; he catches unionizers gathering, but lets them go; he and Regus (who has remembered his farmer's roots and changed allegiances, too) secretly truck in supplies for the miners' families, evicted from their shacks after a strike; a "Squatterville" grows up on the Bones' property -- and the story ends in an explosion of tragedy and a long aftershock of sorrow.

All this is told in a flexible and laconic colloquial prose that also functions beautifully when Yount subsumes Music's thoughts within a compassionate omniscient overview. The style is effortlessly functional. We believe that Yount has absorbed the world of these people, and re-created it with utter empathy and accuracy.

"Hardcastle" can, I suppose, be faulted for its political evasiveness. Its chief Communist organizer is a cardboard bore, and the claims of party rhetoric vs. the unaffiliated working-man's appeal for justice aren't really explored.

Yet as a work of traditional fiction with its roots in the basic stuff of our history, this seems to me one of the strongest American novels in some time. I hope it will be considered for the 1981 Pulitzer Prize for fiction.