My answer is 'yes' and before all my Christian readers go ballistic, please continue reading! First, I'm going to qualify my answer by putting it into the right context. I'm talking about Christian fiction and the fact that some authors feel compelled to include every aspect of the 'message', despite the fact that this may not be the best way to get that message across.
First and foremost, authors need to consider their audience. If your audience is primarily a Christian one, then topics of a spiritual nature and references to the Bible are totally in order. However - and this is a BIG HOWEVER - if this is the case, your readers don't need to know a step by step method of how to give their lives to Christ, nor do they need to read every scripture typically related to this event. They probably know this already! These details tend to slow the story down, and unless your objective is putting your readers to sleep, skip them!
Ah ha, you say. But my main objective is to win the lost for Christ. Fine. This is a valid reason for writing. Many authors feel God has given them a story and it is their duty to write it. Consider, however, that if your audience is mainly non-believers, you have to make them want to read your book. Your God-given mission will have little effect if nobody is reading your book in the first place.
My advice is to offer just enough gospel as to titillate, but don't bombard them with it. Statistically, zealots who go door to door with an 'in your face you're going to hell' message get very few real converts. Friendship evangelism, on the other hand, opens the door to sharing your personal story in a non-threatening manner. This is the approach you should take in your Christian book. Don't try to be an expert, sermonize, or fit in too many scripture references. Intrigue them with the gospel so that they will go and seek it out for themselves. You may be interested in an article where this topic is discussed further at 'Pentalk'. While I believe there is a place for overtly Christian writing, make sure it doesn't smother.
Mike Duran, my new favorite voice in the blog-o-sphere, posted a couple of articles recently that address this issue on an even wider scale.'The Problem With Message Driven Fiction' and his accompanying post on 'WordServe Watercooler' highlight the dilemma faced by authors who feel they have a message.
As well, in a previous post, I discussed the place of 'edgy Christian' fiction. Just where does this emerging genre fit into the mix?
In the end, each writer must examine their own motivation for writing. It is my humble opinion that too much gospel in a work of fiction kills the book. I'm not saying that the message itself isn't appropriate and there isn't place for it. What I am saying is, look to your audience. Christians want fiction that encourages them in their faith, not sermons. Non-Christians need fiction that invites them to investigate the beauty of the gospel without trying to convert and disciple all in one go.
I'm sure there are many differing opinions on the topic. I invite your discussion.