Omar Kohn is 15 years old, lives in Charleston, S.C., and is a junior in high school. The year is 1939. His father, who once ran a prospering business downtown, has been seriously ill for some years and cannot work; his mother, on whom the entire burden of caring for the family has fallen, is close to a nervous breakdown. Omar thinks frequent and ardent thoughts about girls, but is too timid to do anything about them; instead he channels his energies into the summer-league baseball team of which he is captain.

These are the essential ingredients of "Surfaces of a Diamond," the second novel by Louis D. Rubin Jr., University Distinguished Professor of English at the University of North Carolina at Chapel Hill. Rubin is a respected critic and a prominent authority on southern literature and culture, but "Surfaces of a Diamond" is useful primarily as a reminder to those of us who practice the trade that it can be a lot easier to criticize than to create.

In some respects it is an agreeable book; it has an appealing reflective quality, and Rubin's memory of the details of life in 1939 is keen. But he cannot decide whether he is writing a novel or a memoir; the result is a hybrid that manages to be neither, a book without any discernible focus or narrative line.

Rubin clearly is trying to anticipate such comment with a curious aside near the end of the book in which he observes: "I once wrote a novel, about 20 years ago, in which, although I drew heavily upon a remembered time and place, almost everything that actually happened in it was made up, invented out of the whole cloth. The following year I was chagrined to find that The New York Times Book Review had listed it as recommended summer reading under the category of 'Memoirs.' " He goes on to say:

"Far back along the way, the protagonist of this story took over his own direction . . . I have only a general idea of what the meaning of what he does is going to be . . . I shall not know for sure until he actually does it. My task has long since become principally that of deciphering exactly what it is that he wishes to do."

But Omar Kohn conveys little sense of being a creature of Rubin's imagination; everything about his life is recorded in such a literal, matter-of-fact way that Rubin gives the impression he is making comprehensive notes from his own life. A great deal of information is recorded; some of it is interesting, but much of it just squats there to no apparent purpose. A typical passage:

"Saturday afternoon Tommy Rittenhouse came over to our house and wanted me to catch baseball with him. I got my first-base mitt out of the closet, and we walked through our yard and over to his house. We never threw baseballs in our yard, because my father was afraid a ball might get away and hit one of his temple orange trees or rosebushes. I did have a basketball backboard in one corner of the yard, but that was permissible, because the ball never went very far. We took up stations in Tommy's yard and began loosening up, tossing easy at first and then harder. After a few minutes Tommy began spinning a few curveballs. He had a pretty good curve, though because of his size -- he was only about five feet four inches tall, considerably shorter that I was -- he could not throw with too much velocity. I could handle anything he threw with my first-base mitt."

The passage illustrates two of the novel's chief problems. One, obviously, is the plodding accumulation of detail; most of what Rubin puts into that paragraph has no real bearing on the development of the novel, the establishment of the scene or the delineation of character. The second is that although the book is written from the vantage point of adulthood, it is spoken in the language and tone of adolescence; the entire book, like that passage, reads as if it were a dutiful report entilted, alas, "What I Did on My Summer Vacation."

What Omar Kohn did was to experience a number of entirely predictable rites of American adolescence. He goes through a period of tension with his parents, but ultimately rediscovers his love and respect for them. He learns a lesson about adult duplicity and selfishness from the coach of his baseball team. He imagines himself a budding journalist, but is brought up short when he mishandles an assignment for the high-school newspaper. He works up the courage to ask a pretty girl for a date, and finds that she is genuinely interested in him.

All of this is pleasant enough, but there is nothing to make the reader follow the tale through to its conclusion. The lessons Omar learns are good ones, and the pride in his family that he develops is touching, but there is no dramatic or psychological tension attended to these discoveries. Perhaps Rubin would contend that life itself is often like that, which is true; but fiction must be constructed around something, and "Surfaces of a Diamond" has no center.

One final comment. American fiction of the 20th century is already blessed to excess with novels about the anguish and ecstasy of male adolescence. Writers started repeating each other at least a generation ago, and that pattern rarely changes. Louis Rubin, for all his obvious sincerity, adds nothing new to the genre.