BOOK REVIEW / FICTION : A Trip to Discovery and Peace of Mind : NO ONE BUT US <i> by Gregory Spatz</i> ; Algonquin Books of Chapel Hill $17.95, 224 pages

Although the road novel isn’t the exclusive province of American novelists, the genre flourishes here, perhaps because our vast transcontinental distance offers the writer far more scope than, say, a journey from Paris to Lyon or from London to Dublin.

Driving from the East Coast to the West, either alone or with a significant other, provides a suggestion of structure. Our empty plains encourage introspection in a way that a string of European villages and towns can’t match. With any luck at all, an entire novel can take shape by Denver.

Spatz has made his journey both emotional and actual. “No One But Us” is essentially a two-part book. The first section chronicles an extraordinary period in the life of the then-15-year-old narrator, Charlie.

His parents are divorced and his mother is in the hospital with a badly broken thigh and damaged vocal chords--injuries suffered during a suicide attempt.

Recovering from what was apparently and fortunately only a half-hearted try, Charlie’s mother arranges for her son to live with Jolene, her best friend.

Jolene, 26, single and fun-loving, may not be the ideal guardian for a teen-age boy, but there are no other options. Nothing is supposed to happen, but everything does, immediately.

Charlie falls completely and totally in love with Jolene, and she responds to him with equal intensity. He’s mature for his age; she isn’t, and in every respect but chronology, they’re a splendid match.

The affair is intense but brief. Charlie’s mother returns home, having more or less learned to cope with her problems, and Charlie and Jolene can meet only occasionally.

“For an afternoon and a night, or sometimes just a night, Jolene and I would pretend that time had doubled over on itself. We would imagine that we were as close as we ever had been, and as close as we used to imagine we always would be.”

Charlie is expected to take up his schoolboy’s life where it left off--sports, buddies, giggling sophomores, exams and all. In a matter of weeks, he had been transformed from child to man with virtually no adolescence.

Until Jolene, Charlie’s entire sexual history consisted of kissing one girl a year earlier at a birthday party. After Jolene, it supplies the entire first half of this book. The spring following the fateful fall when they had lived together, Charlie and Jolene manage a trip to Lake Erie, which they both realize is probably their last adventure.

Jolene leaves town without telling either Charlie or his mother, and they won’t hear from her for three years.

Charlie tries to turn himself back into a kid, but it isn’t easy.

Working as a lifeguard at the local pool, he watches a couple of girls his age eyeing him, “burning in the sun and sweating through their towels. . . . That’s when it hit me that Jolene was really gone. That was when I knew how long it would be before I ever got past any of this.”

We catch up with him at 21, living near Philadelphia and working in a suburban clothing store. Charlie’s mother has finally received a letter from Jolene, who is now living in San Francisco. Jolene has asked about him, it seems, but that’s only part of the message. She’s living in a communal house, and, for the moment at least, has switched her sexual interest from men to women.

Naturally, Charlie is unsettled by the news, and conceives the idea of buying Jolene a Christmas present.

The colleague who rings up the purchase is an attractive young woman interested in Charlie, but even more fascinated by the potential recipient of the gift.

Charlie and Angel begin an affair, during which Angel becomes so obsessed with the mysterious Jolene that she initiates the drive across the country to deliver the gifts in person.

Charlie agrees, and the resulting hegira is an American road novel in its purest form. The narrator finds himself, comes to terms with his past and his future, but still manages to surprise and please the reader along the way.