"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!"

To urbane readers, that may seem a small innovation. To some Christian readers, it may seem a shocking one. For the future of the genre, it is completely necessary, not only because it allows writers to portray life as it is lived, or to drive sales by being "edgy"-it allows them to deal with sin. For if you can't portray sin, how can you portray the saving power of the Gospel? Vinita Hampton Wright's "Velma Still Cooks in Leeway," one of the most successful Christian novels from a literary point of view, illustrates this point: there may not be any cursing, but there's rape and abuse and startling brokenness. And that plainspoken, hard context makes Wright's presentation of the Christian life all the more compelling.

The real change in recent Christian fiction is not merely the appearance of the occasional profanity, but a revolution in plot. Pick up a Christian novel published as recently as five years ago, and you are likely to find a story whose plot line turns on someone's conversion. This is the old, old story American evangelicals have liked to tell best: the tale of a sinner whose heart is "strangely warmed" (in Methodist founder John Wesley's phrase), who repents and commits his life to Jesus Christ and is born-again.

Conversion remains the backbone of evangelical stories, but frequently Christian novels being published today tell what happens after the conversion. Their stories concern the messiness of everyday life. "It is good to see Christian fiction become less dogmatic and overt, and offer much more ambiguity and the friction between life and faith," says Dudley Delft, fiction acquisitions editor for Waterbrook Press, the Christian arm of Random House. "That friction is where most of us live. Why shouldn't fiction reflect that?"

In a recent novel from Nelson's Westbow, "Savannah from Savannah," first-time novelist Denise Hildreth gives us a modern, Southern coming-of-age story. Savannah from Savannah is a 24-year-old journalism school grad who returns home to write for the local paper and is assigned to dig up dirt on the Miss Georgia pageant. But the heart of the novel is Savannah's mother, the wonderful, fearless Victoria (call her Vicky at your own peril). High-heeled and made up by 7 o'clock each morning, Miss Victoria is the bane and blessing of Savannah's life, and Savannah's homecoming is a piercing tale of mother-daughter love, reconciliation, and growing up.

Is "Savannah from Savannah" Christian? Well, sure. Savannah goes to church, prays a lot, jogs to Christian rock 'n roll, and is well on her way to becoming a new creature. But Hildreth doesn't give us any road-to-Damascus conversion scenes, just real life. The characters are far from perfect. They are needy. They are flawed, with their flaws on full display. And they happen to be Christians.

Christian publishers still have their limits. Penelope Stokes's delightful new book, "Circle of Grace" depicts the lifelong friendship of four women who work through the everyday dramas and difficulties of home, family, and marriage-standard fare these days for Christian publishers. But Stokes includes a discussion of lesbianism, which is not. Stokes chose to publish with Doubleday.

If it seems that most of the development in Christian fiction has come in women's fiction, that's because women's fiction is booming in the mainstream as well, creating a parallel hunger in the Christian market and improving the odds of a crossover hit. A similar "echo" boom has appeared in Christian chick lit, which has exploded. The second in Kristin Billerbeck's Ashley Stockingdale series, "She's Out of Control," chronicles the sagas of Silicon Valley singletons. Christian publishing giant Zondervan also recently published two Bridget Jones-y novels by Penny Culliford, "Theodora's Diary" and "Theodora's Wedding."

To dismiss these novels as derivative is to imply that general fiction doesn't capitalize exhaustively on every new trend (including Christian novels). The more damning criticism is that Christian industry has yet to produce a novel that is uniquely Christian, presenting the full truth of evangelical experience the way, say, Jeffrey Eugenides, who won last year's Pulitzer for fiction with his book "Middlesex," captured in his story of a young hermaphrodite the acerbic, postmodernist culture.

But that Christian writer is out there somewhere, and when he or she rises it's more likely than ever the breakthrough won't be languishing on a shelf in a Christian bookstore, but will be stacked in the window of your local Barnes & Noble.