FIRST LIGHT By Charles Baxter Viking. 286 pp. $17.95

WITH TWO volumes of short stories to his credit and a Guggenheim grant in his pocket, Charles Baxter is an established young American writer. Perhaps for that reason he has taken an awful chance with his first novel -- telling it backwards. The reader comes to know Dorsey Welch and her brother Hugh by accompanying them back through time, from their present status as wage-earners and parents to the primordial moment when a solemn 5-year-old touched his newborn sister's hand.

Only a virtuoso could manage such a narrative, and Baxter is and does. There may be a drop in dynamism from the novel's first long section to its brief final vignettes, but at the same time there is a photo-album fascination in seeing adults as their own childish predecessors. And the reversal mirrors the direction of Dorsey's work: she is an astrophysicist pursuing starlight back toward the "first nanosecond" of existence, right on the heels of the Big Bang.

This unraveling of the present enables Hugh to recapture lost prowess. Now a Buick salesman living with his placid wife and their daughters in the Michigan town -- in the very house -- where he and Dorsey grew up, he was once a gilded youth whom boys hung around and girls fell into bed with. Never a scholar, though. Dorsey's mind was always flash-quick, and Hugh fell into a familial matrix: she was the brain, he the jock. Over the decades -- Hugh seems in his early 40s -- his universe has dwindled while hers -- through the birth of Noah, her illegitimate son; through marriage to Simon O'Rourke, a dazzlingly eccentric actor; and through the theorizing that drives her career -- has expanded, become, in a sense, The Universe.

All of this is told in the same lambent style that graces Baxter's stories. Wit is one of its hallmarks. Simon is an anti-handyman. The last time he tried to fix the car "it had to be towed to a certified mechanic, who smiled shrewdly and wiped his hands in a predatory manner when the hapless car was pulled into his garage." But when it comes to canny assessments of people around him, Simon has few peers. This is his reaction to learning that stolid Hugh has just come down from the roof: "Every man wants to climb onto the roof of his house. It makes him feel like a homeowner and a desperado, a perfect and impossible combination."

SIMON, in fact, is the novel's crucial character. Noah, who is deaf, adores him for his gentleness and animation. Dorsey, though disconcerted by his sporadic sleeping around, finds him enthralling and sustaining. Hugh can hardly stand him. Simon personifies the extent to which brother and sister have drifted apart despite their best intentions and in the face of Hugh's promise to their parents, who both died young, that he would always take care of Dorsey. "Can brothers and sisters get divorces from each other?" Dorsey asks Hugh at the story's front-of-the-book ending. "I think they can, and I think we got one."

To read First Light is to refresh one's faith in patterns. However one ultimately rates Baxter's last-things-first method of narration, there is no denying its formal power. His characters, too, embody a quest for cohesiveness. Dorsey works on equations she hopes will show the the universe to be continuous, will lead her anywhere but to "naked singularity," with "all matter and spacetime compressed to a point." The problem with singularity in astrophysicists' lexicon is its utter disconnectedness; the problem with a universe reduced to singularities is that there would be nothing comprehensible left in it, not even a bare-bones record that it ever existed.

Dorsey's anxiety harks back -- which is to say forward in the book -- to a scene in which Hugh once confronted his father with his habit of daydreaming. "I have this feeling, kiddo, that there's an order to things," Mr. Welch explained. "Everything on earth is what it is and something else. Everything gives off a signal. Most people never hear any of it. Their ears are closed . . . It's like music, but it isn't music, it's an overtone. Dorsey hears it. It's an order. Do you know what I mean?" Hugh's tragedy is that he doesn't hear the tone but knows exactly what his father means.

The world of letters has ample room for a book or two that runs end-middle-beginning. But First Light is more than an oddity. In delving back through the Welch archives, Charles Baxter has unearthed new insights into the strengths and limits of family ties.

Dennis Drabelle is a Washington writer and editor.