An exile goes back to Ireland; Home Before Night, by Hugh Leonard. New York: Atheneum. $9.95.

"Home Before Night" ventures into the territory of author/playwright Hugh Leonard's recent Broadway success "Da," giving us a wider view of his Irish homeland and compatriots than did the play.

Not only do we find Leonard's wry and silly Da here, but also his grandmother , mother, neighbors, friends, and employers.

He guides us through his childhood in Dalkey, a village just south of Dublin, during the economically depressed 1930s, through maturity in the war years, to his decision to leave Ireland in the late 1950s after 14 years in the civil service. Much of the memoir recalls the Joycean archetype -- the young artist struggling to escape family, religion, and social mores -- to escape Ireland itself in order to survive.

Some of Leonard's passages make one laugh aloud. His social comedy arises from a number of dissociations. Perhaps the most obvious and pleasing lies in the elaborate texture of his formal prose, which slides incongruously into the colorful "begobs" and "bollixes" of working-class Dublin slang. In addition he has a remarkable gift for extravagant comic simile ("trying not to offend him was like crossing a minefield on crutches"). And throughout most of the memoir Leonard refers to himself in the third person, a distancing device that separates the childhood of John Keyes Byrne (an adopted child, like Joyce) from his later life as a professional writer with the pen name of Hugh Leonard.

Despite the comedy, a good deal of pain seeps into all these fissures, and Leonard doesn't disguise it. In large measure, Irish comedy is the comedy of pain. Seven centuries ago Ireland lost her equilibrium in the Norman Invasions and has been fighting to regain it ever since. Any recovery of national language, custom, or identity will be partial; only territory can be fully reclaimed. The rest is lost to tragedy.

The preponderance of the book has tragic overtones: recollections through a child's eyes of the mortifying public displays of a drunken mother, the savagery of priests in the classroom and confessional, the twisted lives of relatives, neighbors, and friends, and the broken genius of Mr. Drumm, Leonard's civil service mentor and the subject of his new play, "A Life." As Leonard observers, "The Irish love failure."

But despite its pained moments, this story is not a tragedy. In 1970 Leonard settled with his wife and daughter back in Dalkey, no longer a blighted town, but a fashionable suburb. The Ireland of a failed generation is gone, and with it the tragic world of parochial hates, infantile morality, and appalling poverty. What once threatened the very existence of Leonard's genius (and he has considerable genius) now nourishes it. You canm go home again, he finds.

This is a tragicomedy, then, of the survival and recovery of an adopted son who, unlike Joyce, did return home, a celebrated artist in his own country, in his own time. And this may be the rarest of all Irish comedies, a comedy of forgiveness.