Those few links in my last non-fiction post (and here's another for good measure) have highlighted one thing: it appears to be a widely held view that there is very little Christian science fiction available, or that the genre begins and ends with the esteemed Mr Lewis.
If you've been here a few times - and especially if you've checked out the Elliot List - you will know that this is not necessarily the case. However, I think this depends a great deal on your interpretation of what 'Christian fiction' actually means. I had a stab here, and there's a reasonable list of Christian elements here.
Until I began looking a little harder, started this little blog, and encountered the Elliot List, I was guilty of the same kind of ignorance. I had discovered Stephen Lawhead, Chris Walley, and of course CS Lewis - all in Christian bookshops - but was largely ignorant of what Christian elements may exist in secular sf novels. Only a further reading of some of these stories will tell whether (IMHO) they cut it as 'Christian' novels. I suspect that if an author is writing from a Christian worldview, and including an element of spirituality in their tale, the Christian element will be visible to those looking for it.
It is, of course, possible to portray Christianity in a negative light (as in His Dark Materials), or as an integral story element without actually adding anything to the reader's faith (Snow Crash, reviewd here recently, has an integral religious thread, but I would never consider it a Christian novel).
My best guess is that if people want Christian fiction to challenge them and make them grow in their faith, they may be largely restricted to what's in the Christian bookstores (although there will always be exceptions picked up by mainstream publishers) and as far as sf goes, that's a pretty limited choice.
The question is, What do we hope to gain from reading a Christian novel?
I'll leave that one open to the blogosphere.