As a comedy routine about the absurdity of religious fundamentalism, Bill Maher's "Religulous" is very, very funny. As a serious discussion of religion and spirituality, it is, well, very, very funny.

This film needs to come with the right consumer label, such as "irreverent comedy" or "politically incorrect sermon." Anyone anticipating an in-depth look at how world religions go wrong or the failure of God in the modern age will be genuinely disappointed. As it stands, "Religulous" acts as a litmus test: If you love it, you're undoubtedly an agnostic secular humanist. If your blood boils, you're deeply religious.

Lionsgate unveiled the provocative film in Toronto, and it now opens an almost-secret Oscar-qualifying run in New York and Los Angeles.

As a political humorist, Maher has never been afraid to offend. In fact, he seems to relish it. He just can't resist that final smart-alecky remark that skewers an opponent. Here, in his first major movie project, he travels the globe to discuss God and religion with true believers, challenging their interpretation of various holy scriptures and trying to understand — or at least pretending to try — what underlies fervent faith absent any proof of God's existence.

For the second straight movie, director Larry Charles has made certain his cameras are in the right places and let his "lead actor" run away with the show. And like Sacha Baron Cohen in "Borat," Maher absorbs the limelight as a baby does his lotion.

Maher begins with a family revelation: He grew up Catholic, but his mother never went to church. Turns out she is Jewish. Of course, the family left Catholicism long ago — something to do with birth control, she thinks — which leaves Maher in the strong position to attack the entire Judeo-Christian ethos without any implication of bigotry.

He does a good job. The jealous, wrathful God of the Old Testament, the Virgin Birth of Jesus and concept of Original Sin — that last one not in the Bible, Mayer points out — are ridiculed. Clips from old movies illustrate the fallacy of literal interpretations of Bible stories. The Mormon belief that Indians represent a "lost tribe of Israel" juxtaposed with Mel Brooks' Yiddish-speaking natives from "Blazing Saddles" is particularly effective.

The problem is whom he chooses to question and where he chooses to go. For the most part, he verbally jousts with evangelical charlatans and redneck whack jobs. He visits a Holy Land theme park and a Creationist museum.

Maher doesn't risk questioning a learned theologian or even a devout Christian or Jew who reads the holy scriptures as a spiritual guide without having to accept as literal truth stories written by men 2,000 years ago. William F. Buckley was still alive when this movie was made. Wouldn't you like to see Maher take on him? Nor does Maher acknowledge the deep divisions within many religions over issues like homosexuality.

Maher reserves his sharpest and most passionate outrage for politicians who wear religion on their sleeves like Boy Scout merit badges. An interview with Sen. Mark Pryor, D-Ark., certainly makes his point, more than the senator might have realized.

But by focusing so narrowly on religious fundamentalists and bigots while ignoring any spiritual dimension to religion, the film not only is being disingenuous but limits its audience to nonbelievers. The fact remains, Maher is preaching to the choir.