THE CONGRESSMAN'S DAUGHTER. By Craig Nova. Delacorte/Seymour Lawrence. 301 pp. $16.95.

THE CONGRESSMAN'S DAUGHTER is the fifth novel by the immensely gifted Craig Nova, and by a considerable margin his best. Its characters are strong and various, its setting is palpable, its themes are carefully woven into an unfailingly interesting story. Its prose, by sharp contrast with the self-consciously literary style of Nova's previous novel, The Good Son, is lean and, when required to be so, powerfully descriptive. Though it has a problem with narrative point of view that occasionally distracts the reader, it is a highly accomplished book that should greatly strengthen Nova's reputation and bring him a larger following than he has thus far enjoyed.

Let's get that problem out of the way at the outset. The Congressman's Daughter is the story of Alexandra Pearson, who is 19 when we meet her and 37 at the novel's conclusion; telling her story, needless to say, involves describing her most intimate thoughts and actions. The narrator, though, is neither Alexandra herself nor an omniscient author but an elderly man, a close friend of the family whose name is never given. As it happens he is a thoroughly engaging fellow, but at too many points in the story it is simply impossible to believe that he knows as much about Alexandra's most private life as he claims. True, he and she are close friends and they have many long, intimate conversations; but too often Nova grants him an omniscience that strains credulity and therefore calls attention to itself.

That having been said, my advice is to suspend disbelief and let Nova tell the tale on his own terms, because he manages to rise above the difficulty he has created for himself. Apart from this single misstep, The Congressman's Daughter is the work of a writer in control of his material and able to imbue it with genuine urgency. In Alexandra Pearson he has created a woman of great character and resilience who -- except for her considerable wealth -- could have been invented by Thomas Hardy: a Sue Bridehead or Tess Durbeyfield, struggling against the constraints of conventionality, longing to escape from the narrow role to which society has consigned her and to let her passions have free rein. Like Hardy, Nova writes sympathetically and confidently about women; Alexandra Pearson is one of the more memorable characters in recent American fiction.

As the novel opens she is returning to her home in southern New England. Some time ago she ran away to California; now she is pregnant, and has come to ask her father's help. He is Harlow Pearson, former congressman and widower, a charming but stubborn and domineering man who knows, though Alexandra does not, that he is about to die. He offers assistance, but on difficult terms. Then he dies -- "The dirty son of a bitch," Alexandra says. "I loved him so much" -- and in his will confronts her with even more difficult terms. These, though they permit her to have the child, lead her into a distasteful marriage of convenience to Bryce McCann, who had been a legislative assistant to her father in Washington and had insinuated himself into the old man's confidence; leaving Alexandra little choice except to marry Bryce -- a congenital liar and cynical manipulator -- is Harlow's way of controlling her life from the grave.

For the sake of Anne, her daughter, Alexandra capitulates; she and Bryce establish a chilly modus vivendi under which he spends most of his time in Boston, womanizing and managing his share of the family fortune, while she and Anne idle the hours away at the isolated Pearson residence. She seems "condemned to those long, quiet evenings, to the lonely teasing, those hours that promised so much and gave so little," but within her there burns an unquenchable desire to break away that finally cannot be denied: "She was thirty-seven years old and had every reason to be impatient. How much life was she supposed to let slip through her fingers before she came to the point where she didn't give a damn and pushed the liar on his long slide into hell."

WHEN PUSH comes to shove, the results are not pretty. First, Alexandra realizes that Bryce is attempting to arouse her daughter's sexual interest; this soon leads to Anne's precipitous departure for college. Then Alexandra begins an affair with a working-class man she has loved since childhood, Willie Shaw: "Was it a crime to want to be touched, or to have some small, decent thing of her own?" Bryce learns what she is doing, and sets out in malevolent pursuit of the couple. This extended scene, brilliantly described, ends in a terrible confrontation during which Bryce suddenly realizes that there is nothing Alexandra will not do in order o be rid of him; she no longer can be controlled by anyone except herself.

Alexandra's escape is not merely from Bryce, but from the web of lies that has been wound around her: the lie of her marriage, the lie that Bryce is her daughter's father, the lie that she is happy, the lie that Willie is wrong for her because he is of the wrong class. Hers is not a "liberation" in the conventional feminist sense -- though what has been done to her has been done, by and large, by men -- but a refusal to be bound any more by the self-interested demands of others. What Alexandra Pearson decides at the end is simply that she is going to be herself, whatever risks that may involve.

These risks are considerable: standing up to the memory of her father and the presence of her husband, but also defying the rigid social stratification of the town. As much as anything else The Congressman's Daughter is a novel about the dirty American secret of class: how it is established and perpetuated, how it alters and even destroys people, how it can color the most intimate aspects of their lives. The victory that Alexandra finally wins is certainly a triumph over the lies and manipulation to which she has been subjected, but it is also one over class -- a more substantial victory, it must be said by way of rounding out the comparison, than Hardy allowed any of his redoubtable heroines.

At one point when things seem especially bad Alexandra tells her old friend: ". . . was it so bad that she wasn't able to give up hope? It's all she had. . . . Where did that hope come from? she wanted to know. It was hard to give it up. That was the problem. She said it was hard to live without it." Her story is evidence enough that hope need not be merely empty; combine it with passion and will, and you can change your life.