For established mainstream publishers and distributors, the Christian market has become too big -- and too lucrative -- to ignore. Last year an estimated $4.2 billion in Christian-oriented books, music and other forms of entertainment was sold, often in Christian superstores, according to the CBA.

Publishers Weekly, the book industry's trade journal, reported last year that religious titles were at the top of its annual lists of both best-selling fiction and nonfiction for 2001, the first time that had happened.

This growth has led to a sometimes uncomfortable marriage of the sacred and the secular. Contemporary Christian music companies, once independent, have been bought by huge music conglomerates like BMG. Time Warner (owner of HBO, the television home of the gleefully vulgar ''Sopranos,'' ''Sex in the City'' and ''G-String Divas'') has an evangelical division for books, based in Nashville, that includes the Warner Faith imprint, specifically for Christian audiences, and Walk Worthy, for Christian African-American audiences. Rupert Murdoch's News Corporation owns Zondervan, a Christian publisher. Ruder Finn, the public-relations firm, promotes religious titles through a specialized division.

Michelle Rapkin, director of religious publishing at Doubleday, had made plans to publish ''Circle of Grace,'' a new novel by Penelope Stokes, next summer under two imprints: Doubleday and Waterbrook, the religious imprint of Random House. But a few weeks ago, Ms. Rapkin said, Doubleday decided to publish ''Circle of Grace'' alone. There were two problems with the novel for a Christian imprint, she said. One of the characters, a young woman, becomes an Episcopal priest. Another character, a middle-aged woman who undergoes therapy and discovers she has submerged her personality her entire life, unleashes her fury in salty language.

''It probably wouldn't shock you or me or very many people, but there are those who don't want to see it on the page if it has the Christian stamp of approval,'' Ms. Rapkin said, calling the necessary line ''a tightrope.''

Two years ago Doubleday tried to capitalize on the success of Philip Yancy -- who has sold five million books in the Christian market -- with ''Soul Survivor,'' his 15th book, as a mainstream title. While it was hardly a disaster at 110,000 copies, the publisher was disappointed. In paperback it will appear under both the Doubleday and Waterbrook imprints.

Still, many Christian book and music titles have become huge successes in the mainstream world, available also at Barnes & Noble and Amazon.com. Some classics, like ''Lord of the Rings,'' find a warm reception in the Christian market, and many writers and musicians, like the novelist Jan Karon or the singer Amy Grant, cross over to the secular side.