The entertainment landscape these days is crowded with books, movies, and television shows that feature spiritual story lines and Christian characters. The trend began more than a decade ago, with a couple of prominent television series. But it has really only been within the last year or so that the entertainment industry "got" religion.

Not all of the religiously themed productions coming out of Hollywood have been warmly received by the religious community. Take for example the NBC miniseries, Revelations, which was broadcast in April. The storyline supposedly drew upon the biblical Book of Revelation, which describes the tumultuous period Christians believe will precede the Second Coming of Christ.

Fifteen and a half million people watched the first installment in the series, but the storyline was quickly panned by Christian leaders as inaccurate and sensationalized, and by the time the final episode aired, only about 7 million people were watching.

But then there is Ridley Scott's new movie, Kingdom of Heaven. The film is about the Crusades -- a touchy subject some people worried would offend Muslims around the world. The movie has been praised, though, by the Council on American-Islamic Relations, and in spite of some misgivings expressed by historians, Kingdom of Heaven has hit the box office jackpot.

So what is fueling this plethora of religiously themed entertainment? everything from books like The Da Vinici Code, which explores Jesus' Last Supper, to television shows like Book of Daniel, which will debut later this year and feature an Episcopal priest who has conversations with Christ?

"I think that the interest has always been there, but that the products have not always been there," says Jana Riess, religious book review editor for Publisher's Weekly. "When one product is vastly successful, that success breeds success."

Ms. Riess has written extensively on the topic of religion in popular culture. She says the book publishing industry started to recognize as early as the 1990s that the religious -- and specifically, the Christian-market in the United States -- was a big one, thanks to the success of the "Left Behind" series. Those books are a fictionalized account of the Second Coming of Christ, and more than 16 million copies have been sold so far.

But according to Jana Riess, it was not until last year that Hollywood started to recognize the potential of the Christian market -- in large part because of the success of Mel Gibson's The Passion of the Christ, a film that had a hard time finding a distributor. "Hollywood was very resistant to doing a film that was so specifically Catholic, that was going to be very violent. All of those things were perceived as obstacles," Ms. Riess says. "But Mel Gibson was a pioneer, and it's very difficult to be a pioneer. But of course, now that he has had this tremendous success, suddenly everyone else wants to get on that bandwagon."

That bandwagon, according to Jana Riess, has become increasingly denominational. She says the entertainment industry used to shy away from what she calls a specific "faith location". TV shows like Highway to Heaven, popular in the 1980s, and Touched By an Angel, which aired in the 1990s, never told viewers anything about the faith traditions the characters were drawing from.

Now, though, there is a devoutly Catholic president on the show, The West Wing, and Jana Riess says Americans can expect to see more of this. "Hollywood is starting to realize that they don't necessarily have to stand back and be so bland as to say nothing. They can take some sort of more specific approach to this, and that that will speak to the American people."

In order to do that, Hollywood is going to need writers who can appeal to the secular mainstream, but are also familiar and comfortable with religion. As the producers of Revelations discovered, it is not enough just to mention "God" or "Jesus" in your script. You have to get the story right, and that is where groups like Act One come in. Founded in 1999, the organization trains Christian writers to create entertaining and marketable screenplays.

"Some of our students and some of our faculty hope to write characters who are Christian, as so many people in the audience are, and yet who behave as real human beings," says Chris Riley, writing director for Act One. The program stresses the need to create characters who, according to Mr. Riley, "aren't little commercials for Christianity, but who are just interesting characters who have this part of them which believes in God, and specifically Jesus."

While the Christian market may be big, Chris Riley says, it is also quite diverse. And it would be a mistake for Hollywood writers and executives to assume that just because a character is Christian, he is going to appeal to a Christian audience. Storylines that are preachy and characters who are one-dimensional aren't entertaining, according to Mr. Riley. And when all is said and done, entertainment -- and the money that entertainment can generate -- is what Hollywood is about.