Fiction authors must write with a very specific audience on their frontal lobes. They must write for their niche. I've found the terms Christian science fiction & fantasy and Christian speculative fiction, to be too broad.
I'm tired of the debate surrounding "Christian fiction." One side says you must write subtle or secular, and leave your skill to glorify God. The other side insists Christianity must be included in character and plot. I say, every author's fiction-ministry has a different purpose, voice, style, etc. We're like snowflakes—no two are the same. My fiction purpose is discipleship, not evangelism, so I use the descriptor "Biblical."
Sci-fi invokes visions of spaceships and ray-guns. My own dystopian sci-fi is set only thirty years in the future, and focuses on bionics and cybernetics: the fusion of technology and anatomy. This sub-genre of sci-fi is called cyberpunk, but cyberpunk is, by definition, exclusively anti-religion. I've flirted with using the term faithpunk, but I'm not sure it's meaning would click with readers. So, for lack of a better term, my niche is Biblical cyberpunk.
And, while you're at it, read about his Biblical Cyberpunk novel Flashpoint, coming in Septmber 2007.