The Greater the Risk : You have to grow up to discover what’s real : FLESH AND BLOOD <i> By Michael Cunningham (Farrar, Straus & Giroux: $22; 465 pp.) </i>

A Greek-American contractor, crude and demanding. His frigid, refined and lonely wife. Their gay son, defiant and in increasingly violent conflict with his father. A daughter, even more compulsively correct than her mother, who marries a lawyer and flees to suburban respectability. A hippie daughter who flees to the East Village, has a son by one of her drugged-out pickups and contracts AIDS.

American tragedy? Polymorphous cliche? Night-time television serial? And what is it doing in the hands of Michael Cunningham, perhaps the most brilliant of the many novelists who have dealt with gay themes over the past dozen years, and one of our very best writers, in any case, on any theme?

Author of the searing, humane and beautifully balanced “A Home at the End of the World,” Cunningham has now written something more risky and far less balanced. By the time he finishes, he has produced a work of dramatic humanity at a high and poetic level. But to get up to that level--and this is the risk he takes and the price his readers pay--he erects a high ramshackle scaffolding.

For its first 150 pages or so (about a third of the book), “Flesh and Blood” is a novel of unrelieved family dysfunction, with characters and situations that are almost unrelieved cliches. That the writing up to this point is sometimes beautiful almost makes matters worse.

As the children of Constantine and Mary are born and grow up, and the family moves from a New Jersey slum to a New Jersey mansion, we are on a plague ship. Cunningham conducts us through his storm-tossed charnel house wearing an authorial surgical mask. He presents the illnesses not the patients, the ugliness not the ugly, the injury not the injured.

One obvious scene follows the other. Working like a dog to get ahead and feeling unappreciated, Constantine smashes Mary’s Easter baskets. At 8, Billy cries when his father offers to buy him a football instead of a toy horse; at 12, he mocks Constantine’s ignorance of geography and gets a beating; in high school he has a crush on another boy; at Harvard he lets an aging beatnik seduce him. Mary withdraws nervously into shoplifting and pills. Susan, a cheerleader conformist, tests her sexual power on her high school boyfriend and goes home to give her drunk and self-pitying father a seductive kiss. He returns it and keeps after her until she hastily leaves home to get married.

Only Zoe, fey and elusive, stays free. She helps Constantine with his only innocent passion--his garden--and as a child she eludes the bossy Susan by climbing a tree. Almost as if to encourage us to persist through this first unpromising section, Cunningham gives us a taste of the writing he will do later. Her authority flouted, Susan watches her little sister climb. “She believed that Zoe was rising toward an accident more engendered by the sky than the earth.”

It is with Zoe’s lifelong willingness to be endangered by the sky that we move off the scaffolding and into the rich territory that Cunningham begins to explore. His theme is adulthood; growing out of injury and into what may or may not be recovery but in any case, is life. The author’s plague mask drops; the injured and injurers--in some cases the same person--become characters that he nurtures with his gift for the human gesture that offers a human soul.

Billy leaves home in anger, rejects an architectural career because it would please his father, settles to teaching primary school in Boston, and drifts through various gay attachments. After one awful encounter with a menacing pervert, he pumps iron and succeeds in becoming a pseudo-hunk. “He was handsomer now that he had invented a self, settled and sure like a garden devoted to one crop,” Cunningham writes with gentle irony. Billy--now Will--has still not found himself.

Neither has Susan, who lives a correct suburban life with her successful lawyer husband. She has a stereotypical Lady Chatterley affair with her tree surgeon. (Cunningham has several sex passages, all vividly described, though even in the heterosexual scenes it is essentially the male body that provides the arousal.) Conformity is Susan’s revenge on her past, as rebellion is Billy’s, and both are sterile.

Zoe opens herself further and is the first to free herself, though in her case freedom turns tragic. She experiments with drugs and lovers and drifts until an affair with a spaced-out black man gives her both a baby, Jamal, and an HIV-positive reading. By now she has found Cassandra, though.

Cassandra is the vital center of the book, and its agent of transformation. Originally Bertram Butz, she is a transvestite performer--”she” because she feels herself to be a woman in all but the technical sense--who came to New York after a year of graduate school in the Midwest. Had she stayed, she explains, she would have ended up as an effeminate English teacher with crushes on the male students. “Instead of teaching Anna Karenina and Mme. Bovary I wanted to be Anna Karenina and Mme. Bovary.”

Somewhere between Auntie Mame and Divine, Cassandra emerges out of cliche into the author’s wonderfully enlivening instrument. She knows all conceivable kinds of ropes. “Men with dogs are generally trustworthy but no great shakes in bed,” she counsels. She moves in with Zoe to take care of her and become the fiercely protective co-mother of Jamal.

She becomes a comically inspired mentor to Mary, who has divorced Constantine and is trying to learn how to lose her inhibitions, become independent and make friends with her grown children. Cassandra’s toughness and tenderness win her over. The old drag queen, herself afflicted with AIDS, has lessons to impart in the majesty of a woman’s aging, in what to relinquish and seize, in how to act the role you are dealt until you can become it. Cunningham--it is his triumph and perhaps a limitation as well--gives this convert a deeper knowledge of how to be a woman than any of his real women possess.

Mary learns to accept the painful facts of Zoe’s life, to understand Zoe’s own beautifully rendered acceptance--another Cunningham triumph--and to come to terms with her gay son. With Harry, the quirky, introspective, unglamorous man who has become his life partner, Will has grown up. Finally moved by love as well as anger--Cunningham portrays a homosexual love that is as full of peace as of passion--he will even be able to accept his father, if not forgive him.

The author does not overstate or overwrite these changes. In a way “Flesh and Blood” is a thesis novel--it expounds the polymorphous non-perverse--but so were “Gulliver’s Travels” and, for that matter, “Black Beauty.” There was an art, fiery or domestic, to them; and it gave them life not separate from but in partnership with their theses. Mostly this is true of the shining middle and later sections of Cunningham’s book.

Its lingering, narrowing flaw is with Constantine. Richer than ever, he has remarried a tough, self-centered Hungarian. She is the most fully female of the woman characters, yet--is it coincidental?--Cunningham has made her a comic vulture.

Her husband remains the great unforgiven. His children visit him but he is isolated. Will is distant, Zoe is dying and Susan turns against him in a scene of gothic hatred that relieves her but crushes him. His only spark of connection is with a grandson in whom he sees the kind of son he would have liked to have. The hope is ironically and tragically frustrated.

Cunningham’s treatment of Constantine is witty and certainly it has its justification. He has been a disgraceful and damaging figure even as he worked to build a domain for his family that none of them could live in. Most of the evil and pain that they work out of remains with him. Yet perhaps there is more of justice in this and less of understanding than the author has found for the others; as if Adam’s fault, essentially, was in being a father.