2013 saw the 50th anniversary of the death of CS Lewis, that giant of Christian fiction. His Chronicles of Narnia have been made into numerous films and his more evangelical works such as The Screwtape Letters and The Great Divorce have remained Christian bestsellers, as well as reaching mainstream audiences, for more than half a century.
But since his death in 1963, there have been few, if any, Christian writers who have achieved his success, certainly in terms of with intentionally Christian works.
The Christian fiction market did not truly exist in Lewis' day but if he had been able to glimpse the future, there would be very little about the industry that would be recognisable to him. Historical romances, harkening back to a simpler time of bonnets, log cabins and farmsteads, dominate the current landscape of Christian fiction. Any other genre, no matter how popular in mainstream fiction, is relegated to the sidelines.
If you search for "Christian Fiction" on Amazon.co.uk, thirteen of the first sixteen titles Amazon deems as being 'most relevant' are historical or Amish romances.
Visiting the website of a typical Christian publisher, you'll find dozens of titles that fit into the "Amish" or historical - some would say 'bonnet' fiction - market, and their plots will be heavily dominated by romance. But go to the crime section, and you will only find a handful of titles, all cosy mysteries, nothing remotely hardboiled, and science fiction only gets two.
Speaking in Publishers Weekly, Barbra Scott Executive Acquisitions Editor of Abbingdon Press's fiction wing said: "Romance in any form dominates sales, and since 'bonnet' fiction by its nature is a clean read, it remains quite popular in Christian markets."
"Sales of Amish fiction continue to be strong. There used to be one company doing Amish fiction, now there are a dozen. Basically every CBA publishing house doing fiction is either publishing or planning to publish an Amish novel," says Chip MacGregor, president of MacGregor Literary Inc speaking on Crosswalk.com.
According to Grace Bridges, a writer and editor of science fiction in New Zealand who runs Independent Press Splashdown Books, Christian fiction exists within a bubble: "It has very little to do with actual literary merit." Bridges points to the rules many Christian publishers have to keep things as they want them to be: "No dancing or drinking or swearing or card games in some of them. No mention of Catholics or priests. No mentions of underwear of any sort."
J Mark Bertrand, critically acclaimed crime author of the Roland March trilogy, has encountered the same problem. "The Christian publishing world has embraced the safe over the good ... Christian fiction is often marketed as 'if you like this great New York Times bestselling author, you can read this Christian author who is just as good, but the content won't be objectionable to you'."
Author Mike Duran, who has worked with and commented on the Christian fiction market for more than eight years, offers an explanation for why so much historical and Amish fiction gets such a high billing by so many Christian publishers.
"It is a reaction against hyper modernity and hyper-sexuality. Technology is advancing so fast, and there's the pornification of so many things. The whole Amish trend is a reaction against that. It's an escapism to a simpler time, a purer time."
But the reality is that, as Duran puts it, "we want to bury our head in the sand".
"It's not that Amish or bonnet fiction is bad, it's just part of a trend of not dealing with the realities of real life."
The ubiquity of this kind of fiction is described by Chila Woychik, author and editor at Port Yonder Press, as the result of the "tiny vision" of the Christian fiction publishing world. And for good fiction, a wide vision is needed.
The inability to write more varied fiction is representative of a larger problem. Author Sean Lambert explains: "Christian writers need to get beyond their personal censor as well, else they will end up with a very preachy moralistic tale. As Christians we should be, in some sense, un-shockable. Jesus talked to all the people that everyone else avoided. He needs to be our example there."
But when authors try to break boundaries, they're often met with defiance from their publishers, as noticed by Bertrand. "The artistic need is to push back, to say hard truths. Unfortunately the Christian fiction world is not receptive to that kind of combativeness."
Whilst the typical Christian novel may be safe, the lack of diversity can be a hindrance to efforts to affect wider culture. Science fiction and fantasy author Simon Morden recognises that Christian fiction, along with other aspects of Christian culture, can often be seen as dull. "A speaker will come along to the youth group and give a talk about how interesting their life was before they became a Christian, and you kind of wince a little at that, but that's often what it is."
Not only can it be dull, but it can also cause misunderstandings about the real world. Grace Bridges explains. "Often the stories seem like a lot of fluff and they can create unrealistic expectations of life. For example when I was a teenager I was given a box of forty Christian romance novels. And no one thought anything of it, they were perfectly safe, but when you read forty romance novels in a row, you're going to think your life is going to happen that way as well. It's completely unrealistic because they work to a formula. If you take enough of that in, you expect that to happen to yourself."
Bertrand agrees: "They are not realistic representations of the communities they represent. Like Downton Abbey, it's an escape into another reality."
This obsession with safety and simplicity in Christian fiction writing has led us down a path where the novels that are created often aren't very good. Morden points out that "the quality of the fiction becomes secondary" and Woychik adds that, too often, much of Christian writing appears to the mainstream world as "shallow, conversion-centric, laden with too-soft characters and couched in thin plots and flat settings".
Bridges paints the picture of why this is a problem in stark terms. "It's a picture of the bubble that the church is, the enclave of unwillingness to deal with these things."
Says Duran, "Christians are so desirous to get the gospels out there, that we tolerate mediocrity. I think that does a disservice to the gospel. We tolerate mediocrity for the sake of the message."
This all comes together to represent a grave danger, specifically of what Bertrand describes as "a bad witness". If the most visible literary output of the Christian community continues to be poor novels which sacrifice quality for perceived moral integrity, the outside world will think far less of the Church. After all, why would anyone become a Christian if Christianity is represented by mediocrity?