I think there are many books that fit the category of “Christian Fiction” however if there’s not heavy scripture quoting or obvious “religious content” then I think many “Christian Fiction” books could easily thrive in the general market alongside their genre counterparts that are not written by Christian authors. In any scenario I think an author who sincerely believes a certain way and lives out of that worldview is going to have that come through to some degree in their writing and characters. If they just try and cobble in some random worldview because it happens to be what is populsr or will sell books or the editor or publisher wants it that way it soon becomes obvious that things are contrived and awkward to the reader. However when it is part of who they are as a person it flows natutrally into their lives and work and often even someone outside that belief system won’t realize what “hit them” as they are reading because it is simply part of the story.
On the other hand readers see what they want to see or are looking for in a story. If a reader is operating from a specific worldview they often see messages inherent to their worldview in the situations and characters of a story regardless of the author’s intent or belief system. Also I’ve seen readers who will intentionally pick up a given book and look for something to criticize or if they’ve heard the author is a Christian they’ll go looking for the “bible thumping” and even if that wasn’t the point of the story and it may not be all that obvious in the scheme of things they manage to find it anyway. Jesus taught through stories and so do we.
I think if the book was written specifically for Christian readers or goes heavy on the religious content then yes it should be in a separate section where the intended audience knows they can find it and those who’d rather read something different can pass on to something more their style. If a book is written by a Christian from a Biblical perspective and avoids extraneous content such as sex, language and violence unneccessary to moving the story forward then it could certainly be considered Christian Fiction but I’ve seen the label misused going both directions. I’ve seen it applied to books that in my opinion are not appropriate because of extraneous content and I’ve seen it not applied to books that are overly heavy in terms of spiritual content for mainstream fiction. I do think that not putting books where the customer is used to finding them would be detrimental in the long run. In large bookstores that carry a variety of fiction everything is broken down by genre and there is usually a section where specific publishers whose material is primarily for the Christian reader is stocked. These readers know to go there if they are looking for certain authors or something new from a favorite publisher’s line just as a mainstream Science Fiction, Fantasy or Romance reader knows where to go to find their favorite author, series or category line. Now for books that are light enough on content for a mainstream audience to enjoy them for a good story and characters those are great to shove out into their mainstream genre area of the store but authors and publishers should be aware of current trends and fans as well and keep those fans in tune with new releases that might not be in their usual realm of attention. For example if someone was writing Inspirational Romance for a given line and then wrote some clean but much more subtly Christian stories which would appeal to a wider audience and the publisher decides to release them under a different imprint that is mainstream the publisher and author should both promote this information to their existing fan bases.
Personally I don’t look so much at the degree of Spiritual content as at how it is worked into the story like anything that doesn’t move a story forward or seems contrived this will irk me if done wrong. If it flows naturally from who the characters are and with the story itself then it really doesn’t matter. If it doesn’t it still doesn’t really matter how much there is it simply means I will be turned off by a book that could have been executed better and choose not to read it. Like many other elements that I consider extraneous and purposely try to avoid in books by picking material to read I am fairly certain won’t go there, Spiritual content in books can be overdone, contrived or just plain unneccesary and slow a story down or stop it dead in its tracks in these cases I am just as put off as I would be by something I consider inappropriate because it takes away from my ability to enjoy the story and get the most out of my reading experience.