Christian speculative fiction is often about the battle between good and evil. In fact, so is much secular speculative fiction. It's certainly a battle I write about in my own books.
It's also a battle I believe really exists. That being the case, it doesn't seem too likely the enemy would want such literature out in the marketplace, revealing their existence and tactics to whoever. Over the years there has been much lamenting over the fact that Christian fantasy doesn't sell, much talk of what to do to make it better, to get people to read it. But maybe the battle isn't against flesh and blood, but against "the spiritual forces of wickedness in the atmosphere." Maybe, if there really is a battle, books that illuminate it are automatically going to be a hard sell, ignored, overlooked, etc. If there really is a battle, maybe that hard sell should be the expectation, not a surprise.
After all, how do you reconcile the idea of great public popularity for a novel that puts forth Christian ideas with "If you were of the world, the world would love its own, but because you are not of the world, but I chose you out of the world, therefore the world hates you." ("Hates," here, meaning "loves less," or "prefers against.") How does wild and widespread acclaim mesh with Lk 6:26 "Woe to you when men think well of you"?
And what about I Co 2:14 "a natural man does not accept the things of the Spirit of God; for they are foolishness to him, and he cannot understand them because they are spiritually appraised."