It has been four years since Bob Marley, the Jamaican reggae singer and composer, died of cancer at the age of 35. He was a legendary performer and one of the most politically and socially influential popular musicians ever. He was complex but still a man of simplicity. Stephen Davis goes a long way toward capturing his spirit in this new biography.

Marley was born of a white father and a black mother and grew up in the Trench Town ghetto of Kingston. As a Rastafarian, he eschewed meat, read the Bible studiously and worshiped the late Ethiopian emperor Haile Selassie as a god. He smoked marijuana as a daily sacrament and let his hair grow into long "dreadlocks." For Marley, Rastafarianism was a route to black redemption in a cruel, white-controlled society.

Marley gave poor Jamaicans a voice when no one else even knew their language. He wrote his songs out of his past, mating searing lyrics with the bright, loping beat of reggae. "People sensed in Marley's declarations a moral authority," Davis writes.

In 1971 Marley and his band, the Wailers, released "Trench Town Rock," drawn largely from ghetto life. "It turned Bob Marley into a national hero," Davis says. His music was "dark, ominous, threatening . . . a rebel's indictment of slavery and colonialism." He became a spokesman for the poor and oppressed, a "pan-African freedom fighter."

As Marley sought his black identity, his father remained "a memory with which he never really came to terms." Marley tended to think of his father, a captain in the British army who died in 1955, as a representative of Babylon, the Rastafarian term for the corrupt white world. Marley's mother remembers her first husband as "a wonderful person in his way."

Marley's political and spiritual convictions never faltered. When Haile Selassie died in 1975, prompting a Rastafarian crisis of faith, Marley responded with a fervent anthem of religious affirmation. When he was wounded in an assassination attempt in 1976 (thought to have been politically motivated), he performed at a public concert two days later, his chest and arm in bandages. In 1978, with Jamaica in virtual anarchy, Marley brought the country's two political leaders, Michael Manley and Edward Seaga, together on a concert stage, holding their hands aloft in a memorable show of unity. In 1980 Marley and the Wailers performed at the independence ceremonies in Zimbabwe.

One of the most satisfying things about this biography, though, is that for all of Marley's political prominence, Davis never forgets that he was a musician first. He takes us into the lively streets of Kingston and into the studios and rehearsal rooms, where the air was almost sticky with marijuana smoke. He reminds us that Marley was a brilliant composer, combining a melodic gift with a lyrical succinctness that few rock writers have matched. Davis can almost make us hear the Wailers slowly work their way into a song, picking up the complex, asymmetrical rhythms as Marley's supple voice soars overhead.

Davis obviously loves Marley's music, but perhaps he loves it too much. His prose gets overheated, and he seems to find almost every concert "of historic proportions" or "another one of those epiphanic Wailers shows" and too often gets lost in hyperbolic rock slang: "The Wailers were by then so hot, so telepathically on."

The problem with this looseness is that it suggests Davis' judgment is clouded by his adulation. Marley had plenty of faults -- or at least quirks -- that Davis skims over lightly. He was married but slept around continually and had six illegitimate children (plus four with his wife Rita). He was prone to sudden violence. Asked for his views on music or politics, he usually spoke only in the broadest of platitudes and frequently launched into rambling digressions on Selassie and Rastafarian philosophy.

In the last pages of the book, however, Davis turns his sympathy to a poignant advantage. After Marley had a cancerous toe amputated in 1977, he was believed to be in good health. But in 1980 he was found to have a malignant brain tumor as well as cancer of the lungs and stomach. His last months were sad and painful. He went to a controversial clinic in Germany, but in the end no treatment would help. Davis was the last journalist to interview him.

It would seem that Marley got his redemption, though, and that it came in his music, bouncing and free. His life was far too short, but it is good to see him in these pages, defiant and still dancing.