"Christian fiction" is a phrase that has about outlived its usefulness.

Overworked for more than a decade, "Christian fiction" has been asked to describe a dizzying range of books, from Jan Karon's Mitford novels, set in a fictional North Carolina hamlet full of charming eccentrics, to Tim LaHaye's and Jerry B. Jenkins' Left Behind thrillers about the violent run-up to the end of the world. Their success has drawn attention from the tony trade publishers in New York and the big-box retailers. The traditional Christian genres of romance and thrillers have split like hot stocks: there are now "Christian Bridget Joneses," "Christian Michael Crichtons," novels of the abusive and the abused, well-churched and Oprah-ready.

As evangelical writers crash mainstream best-seller lists and mainstream writers hit big with biblical novels like Anita Diamant's "The Red Tent," the line between religious fiction and the other kind grows ever fuzzier. Christian readers, sometimes to their alarm, are having trouble discerning what precisely makes a novel Christian.

For publishers, on the other hand, the category is more meaningful than ever. Today Christian fiction is one of the few growth areas in the industry. Last month's National Endowment for the Arts study "Reading at Risk" showed that the only category of books whose sales have increased over the past year are religious books-of which some 20 percent are fiction-four times fiction's share in the early 1990s.

There has been Christian fiction since long before Karon and LaHaye supercharged sales. Grace Livingston Hill pioneered the genre of Christian romance with "The Chatauqua Idyle" in 1887, and followed it with more than 100 others with titles like "Aunt Crete's Emancipation" and "The Prodigal Girl." Most of them feature darkly handsome men who rescue a sweetly Christian girl from her family's impoverished circumstances. Though her main characters were sterling models of Christian behavior, Hill was strenuously thorough in her descriptions of wicked behavior, and her neat endings usually owed more to Cinderella than Ecclesiastes. As one modern critic reminds us, "Romance novels with some good descriptions of Christians added are still romance novels."

Hill's literary heir is Janette Oke, who published the first of her more than 75 Christian historical romances in 1979. Fantastically popular-there are now 20 million copies of Oke's novels in print-Oke's oeuvre defined Christian fiction until the late 1980s, when Frank Peretti published his imaginative and conceptually interesting novel, "This Present Darkness." Peretti depicted the cosmic battle Christians believe to be constantly raging between good and evil in scenes of muscular Christians literally fending off hellspawn at the back of midwestern churches. Peretti tapped American Protestants' interest in spiritual warfare and foreshadowed the Left Behind craze.

Despite their ample sales, Oke and Peretti were roundly-and, in Christian circles, famously-ignored by mainstream critics and readers. Once the numbers became too big to ignore, and the books themselves started popping up in WalMart and Borders, Christian fiction was dismissed for being too pat, too saccharine, too derivative. Above all, Christian fiction seems too, well, Christian. Its preachiness hits you over the head. You don't feel like you're reading a novel. You feel like you're reading a tract.

Good sales don't trump the plain sense of these criticisms. Neta Jackson's first novel, "The Yada Yada Prayer Group," which, at 100,000 copies, has sold astoundingly well for a first novel in the Christian realm, is a heavily sanitized recasting of Rebecca Wells's "The Ya-Ya Sisterhood." The Left Behind books depend on a theology called dispensationalism that most evangelicals would call extreme, but its broader message that you'd better be Christian or else is more widely accepted-and about as subtle as a Mack truck.

But all that is beginning to change. In January, Thomas Nelson, a venerable Christian publishing house based in Nashville, debuted a clutch of savvy, sophisticated novels from their new WestBow imprint that reflect a Christian worldview, but which don't sacrifice story to evangelism

. "We don't have very strict guidelines about putting evangelicalism front and center," says acquisitions editor Ami McConnell, "and there's no list of words we have to eliminate from our manuscripts." That is, unlike most Christian houses, WestBow might be willing to allow a heroine who has run her car into a tree or sliced her finger with a paring knife to utter something a little saltier than "Oh, sugar!"