The Bible says the truth will set you free. Although "Precious" is based on a novel, it's an act of truth-telling on behalf of a character in hellish enslavement.

In Harlem in 1987, Clareece "Precious" Jones (newcomer Gabourey Sidibe) is at the bottom rung of society's ladder: black, female, obese, illiterate. And at age 16, she is pregnant for a second time by the father who skipped out on her abusive, unemployed mother (Mo'Nique).

As a picture of familial dysfunction, "Precious" is so graphic it makes "The Color Purple" seem like "Snow White." Yet this harrowing movie is likewise a fairy tale, a story of hard-won redemption that's the most powerful film of the year.

When the second pregnancy becomes obvious, Precious is discharged from school and directed to a remedial reading program run by a sympathetic volunteer named Ms. Rain (Paula Patton). The teacher encourages the class of dropouts and addicts to record their feelings in a daily journal.

While her mother insists that school is a useless alternative to cheating the welfare system, Precious can see the faint glimmer of a different life reflected in Ms. Rain and in a tough-love social worker (capably played by deglamorized singer Mariah Carey).

The new life that springs from Precious is a baby boy, healthier than the daughter with Down syndrome who stays with Precious' grandmother. As loudly supportive classmates gather in the hospital, Precious both gives and receives love, at last.

But be forewarned: The ensuing scene in which her mother meets the newborn baby is simply one of the most shocking in the history of American film.

This grim movie would be unbearable were it not for the human gravity of star Sidibe and the artful bravado of sophomore director Lee Daniels. When the neo-realist aesthetic of handheld camera and claustrophobic focus is broken up by fantasy sequences in which Precious imagines she's famous, the movie is outlandishly funny. And some of the scenes with miracle worker Ms. Rain have the sugary sheen of an after-school special.

Yet notwithstanding a last-minute monologue that is likely to win Mo'Nique an Oscar, Precious' mother is so profane and lazy that she redefines the welfare-queen stereotype. And an ostensibly hopeful ending has a huge dark cloud overhead that is barely mentioned.

"Precious" is guaranteed to provoke debate, but as an object of reflection, this rough, hard gem of a movie will have lasting value.