BOOK REVIEW / NOVEL : A Whodunit That Also Offers a Moral Mystery : SNOW FALLING ON CEDARS <i> by David Guterson</i> ; Harcourt Brace $21.95, 368 pages

David Guterson’s haunting first novel works on at least two levels. It gives us a puzzle to solve--a whodunit complete with courtroom maneuvering and surprising turns of evidence--and at the same time it offers us a mystery, something altogether richer and deeper.

In 1954, off the island of San Piedro in Puget Sound, salmon fisherman Carl Heine is found drowned and entangled in his boat’s gill net. It seems to be an accident. Soon, however, darker suspicions bubble to the surface, and a fisherman of Japanese descent, Kabuo Miyomoto, is put on trial for murder.

Heine, the coroner discovers, has a fractured skull; before drowning, he hit his head on something, or was hit. Evidence confirms that Miyomoto boarded Heine’s boat on the foggy night when he died--a rare occurrence among these solitary and self-reliant men. Yet Miyomoto’s initial statements to investigators failed to mention such a visit.

Besides, Miyomoto had a motive for foul play. When San Piedro’s Japanese population was interned in 1942, his parents had nearly paid off their mortgage on a seven-acre strawberry farm bought from Heine’s parents. Heine’s mother, Etta, promptly sold the land to another farmer. Stoic in the face of legalized injustice, Miyomoto and his wife, Hatsue, waited patiently to repurchase the farm when its owner grew old, but instead Heine bought it just before his death.

This is the puzzle: We are led to believe that Miyomoto, who fought with the legendary 442nd Regimental Combat Team in Europe, is an honorable man, although his stern bearing revives anti-Japanese prejudices that nine postwar years have only lightly buried. We are led to believe that distrust of whites--his family and Hatsue’s were shipped to the Manzanar camp in California’s Owens Valley--and guilt over the German soldiers he has killed make him accept his arrest as fate.

But if Miyomoto is innocent, why does a net of circumstantial evidence bind him as tightly as any struggling fish?

Ishmael Chambers covers the trial for San Piedro’s newspaper, which he inherited from his father. A former Marine who lost an arm fighting the Japanese at Tarawa, Chambers was Hatsue’s high school sweetheart; before her crowning as Strawberry Festival Princess in 1941, they secretly met and necked in a hollow cedar tree. From Manzanar, however, Hatsue wrote denying that she loved him, and in the Pacific he felt his love turn into hate.

By now, love and hate alike have faded. “You went numb, Ishmael,” his mother tells him. “And you’ve stayed numb all these years.”

Just as Miyomoto is obsessed with getting back the exact acreage that his family lost, so Chambers sleepwalks through life in the vague hope of reclaiming Hatsue. The contrast between these two obsessions--one conscious and potentially fruitful, the other unconscious and debilitating--is Guterson’s main device for leading us into the mystery.

Which is: How can people in a small, tightly knit community be neighbors for generations, even love one another, yet be torn apart by racism?

During the three-day trial, an epochal snowstorm intensifies San Piedro’s isolation. Island people, Chambers’ father once told him, can’t afford to make enemies.

“No one trod easily upon the emotions of another. . . . This was excellent and poor at the same time--excellent because most people took care, poor because it meant an inbreeding of the spirit, too much held in, regret and silent brooding . . . fear of opening up.” The ordeal of the storm, coupled with the shock of Heine’s death, forces them to confront the past and cracks the ice of their reserve.

Guterson (whose previous work includes a story collection, “The Country Ahead of Us, the Country Behind”) convinces us that he knows or has researched everything essential here--details of fishing, farming and lawyering; of Coast Guard and coroner’s procedures; of Japanese American culture.

With a stately pace and an old-fashioned omniscient voice, he describes the beauty of the Puget Sound islands, the bloody chaos of Tarawa, the desolation of Manzanar and the inner life of every major character.

What he finds there is usually nobility. The only semi-villains are Etta Heine, a couple of FBI men and the anonymous callers who curse Chambers’ father for his editorials defending the island’s Japanese residents after Pearl Harbor.

Everyone else--Hatsue, Heine’s widow, the judge, the sheriff, the aged defense attorney, tough and silent Heine himself--is human and often admirable.

How can so many good people coexist with a major historical evil? The mystery remains even after the puzzle is satisfyingly solved.