FRIENDS ALONG THE WAY. By Julia Markus Houghton Mifflin. 264 pp. $15.95.

FRIENDS ALONG THE WAY is a pleasure: a low-key, intelligent, coming-of-age novel. Betsy Lewis is a 26-year-old American of Italian descent. ("My grandfather crossed an ocean. He disembarked Lupis and became Lewis. Vintage Ellis Isle.") She is living in Rome, married to a rather stuffy representative of an auction house, and spends her days doing research on the Italian Risorgimento. Her existence is pleasant without being too stimulating; she is never in any danger of having a really terrific time.

But then Betsy is brought to life by her friends. She is pulled into a circle of Americans living in Italy by Alice Blanders Russo, an older woman full of quiet charm and ego, an Auntie Mame for intellectuals. "All my conversations with Alice blend; it is as if through the years she has been telling me one story. I hear her voice now, slow, modulated; I hear her opinions, fair and informed; and underneath the pleasant blur, I hear that story. I know we talked about politics that day. And somehow as she talked, softly, steadily, husbands dropped out. I swear I counted three . . . . But she wasn't really beautiful. The more I think of it, I realize it was her very lack of classical beauty that abetted her. You can grow more and more attractive; character piles up with years. A cache. But true beauty has a breaking point."

Betsy's prose here, in the beginning of the novel, reflects Betsy herself. It is intelligent, perceptive, and astringent, as if Betsy is trying to mimic her husband's restrained Boston- Protestant voice, rather than speak in her own New Jersey Italian-Amerian Catholic one. By the end of the novel, Betsy is not merely older and smarter, her style is far more direct: "It's midsummer as I finish this account. Putting it all down has made me feel very good."

Betsy's journey, from America to Italy and back again, and from insecurity to maturity, is an intriguing one. She is drawn first to Alice, and then, even more, to Alice's young lover, Leo Conti, a handsome blue-collar worker and communist labor union official. She writes about Leo objectively -- "He wasn't talented or cerebral or eccentric. He was sexy and he was very nice."

But as the novel unfolds, it becomes apparent that Betsy is not as cool as she would like to be. At first, she recounts the story of Alice's and Leo's courtship in such a removed fashion that she sounds almost like an omniscient narrator. But soon the reason for Betsy's near-omniscience becomes clear. She has memorized every detail of their lives. She is riveted by their emotionalism -- by their battles, their reconciliations, their sexuality.

In the middle of the night, when the two couples are on vacation and sharing a small house, Betsy hears Alice and Leo making love. That's it for her objectivity. Suddenly she is vulnerable, and her description of her friends' passion is both terse and sad.

Betsy's closeness with Alice and Leo makes her recall an earlier friendship. Salmanda Blake, Betsy's girlhood friend from Passaic, New Jersey, is young, gifted, black, and homosexual. That sounds like an intriguing combination, but Salmanda is not as well- drawn as the other characters. She seems more a refugee from a National Brotherhood Week commercial than a human being. Still, when Betsy returns to New York and meets her old friend again, the reader is touched because Betsy is -- and Betsy is such an endearing character.

Julia Markus, who has written Uncle and American Rose, is a first-rate observer. Not only are Betsy and most of her friends masterfully described, but the world they live in feels genuine, three-dimensional. Whether she is writing about Passaic, Greenwich Village, Rome, or Gaeta -- her family's home village just north of Naples -- her prose has texture, authority, and precision.

Friends Along The Way then, is a moving account of a young woman's growing up. It's a quiet book, but Julia Markus doesn't have to make a lot of noise. Her writing is eloquent enough.