As a Christian, if a book is marketed as a "Christian fiction" I tend to stay far away from it because, to me, something that is marketed as Christian fiction I view as aimed at the Christian Fundamentalist community, the folks who take the Bible literally. That's not my reality of my faith. I also tend to look at it as literary pablum, spoon-feeding readers themes and stories that aren't going to cause them to question any mental taboos their faith might have imposed. This is based upon some of the women's fiction that I've attempted that have been labeled as Christian.
Having said that, I did read a couple of mystery books in a series by Mark Mynheir that I enjoyed, and which were the exceptions to my rule. I had to do a review of the first book in the series, "The Night Watchman", and didn't realize that it was going to be marketed as Christian fiction. I was pleasantly surprised that the leading character, who has no belief in any god, wasn't converted by the end of the first book. I'm sure that somewhere along the line he's going to do a 180, but the author was charting a gradual change from disbelief to possibility of belief, which I though was much more realistic, given the circumstances of the character's life.
But because of my preconception of what Christian fiction is, I might not have chosen the book to review if I had know it was going to be marketed that way. Which would have been my loss.