Looking at secular books
You’ll find the Narnia books in Waterstones, but they are outnumbered a billion to one by stories which either deny the spiritual world completely or escape into fantastic realms of pseudo-spirituality.
Is there such a thing as a ‘Christian’ novel? Well, you’ll find a few examples in the back pages of Christian publishers’ catalogues, either romances or lurid portrayals of Armageddon.