THE OBJECT OF literature (we used to say) is to inform or to delight -- ideally both. Sarah Phillips does both. The information it provides amounts to a short course in the life of the black middle class. Its narrator (the title character) comes from a Philadelphia street of large homes occupied by black professionals. Sarah's father is minister of the New African Baptist Church; her beautiful mother, who "knew a bit of French and yards of Wordsworth," is a former teacher. Sarah is educated at private schools and goes to Radcliffe. In our last glimpse of her, she is enjoying a postgraduate year of "experimental naughtiness" in Paris.

What gives social and emotional nuance to this curriculum vitae is Sarah's race. She feels at home in her largely white world, but less in the manner of a native than in the manner of a naturalized foreigner. That makes her a sensitive observer. It is the diver, not the fish, who knows the weight of water.

As to delight: one fairly rolls in some exceptionally lovely meadows of prose. Andrea Lee knows how to say things. Her line is supple, swift, vigorous, full of surprises that at once seem inevitable. She seizes words and orders phrases with that appearance of effortlessness which always characterizes virtuosity.

To illustrate this with brief quotation is difficult. The effect of superior prose is cumulative, like that of compound interest; at first one hardly notices that one is getting an extra return.

But consider the humble matter of punctuation. Consider the colon, how Lee employs it to set off proposition from amused comment. First in this capsule of a 7-year-old: "'Disgusting' was one of Lyn's favorite words: just saying it filled her with such glee that she lay back on the grass beside the curb and waved her thin legs in the air."

And in this of the narrator's cousin: "With girls of any color, Curry was popular: he was the most successful kind of flirt, the kind who really knows about women's clothes, and who can look attentive through long monologues about emotions."

And in this of her mother: "From the dining room, where she liked to sit ironing and chatting on the telephone, came the fragrance of hot clean clothes and the sound of her voice: cheerful, resonant, reverberating a little weirdly through the high-ceilinged rooms, as if she were sitting happily at the bottom of a well."

Only rarely does lovely language descend into precious self-delight, a collapse we can hear in passages like this: "Lounging voluptuously in my underpants on the cool bare expanse of my bed, while flies banged against the screen and greenish sunlight glowed through the shades, I would read with the kind of ferocious appetite that belongs only to garden shrews, bookish children, and other small creatures who need double their weight in nourishment daily."

But if the language of Sarah Phillips is admirable, and its material interesting, there remains the matter of form. And here lies a problem.

This "first novel" is not a novel. Its chapters -- educational episodes with comes-to-realize endings -- are not chapters. They are complete, independent narratives: you could delete any one, even the first or last, with no loss in the coherence of the others. Or slip in additional chapters without even an incision.

If Sarah Phillips doesn't read like a novel, no more do its chapters read like stories. Whatever the degree of imaginative embroidery, the basic fictionality of what we are being told is in doubt. One feels this without any knowledge of the author. It is the writing itself that requires such a view.

Through its shape, narrative tells us what it is, how to read it. Stories compel from us one set of responses, and personal essays (which is what most of these chapters seem closest to) a very different set.

Take death: we feel personally saddened by the death, in the last chapter, of the narrator's father. The death of a fictional character may be sad, but with an aesthetic sadness. And so it is with all the emotions: they have their counterparts in art. There is no confusing our response to real events with our response to events in fiction. Aesthetic feeling is to real feeling as real feeling is to flesh.

This is not, of course, to say that Sarah Phillips should have been fiction; only that these pieces should have been presented -- so that they could have been read -- as what they are. Andrea Lee is a beautiful writer who will get even better. It was wrong to offer her book as a novel, which it is not, and thereby dishonor the good work that it is.