Everybody and their dog knows about Narnia, and has probably read it. They also probably know about the likes of Mere Christianity or The Screwtape Letters. But if you ask them whether they realized that CS Lewis wrote science fiction, they'll look at you like you're from another planet. The Space Trilogy is the unofficial name of his series of Planetary Romance and Fantasy novels, mixing space travel with Medieval cosmology and Christian theology. And... it's C. S. Lewis. Of course it's Christian thematically.