Re-reading "With the Night Mail" made me think of some interesting parallels. Here's my thesis:
Let me explain. "With the Night Mail" and its sequel "As Easy as A.B.C." are great examples of what we in the trade call "worldbuilding." In fact, "Night Mail" does a fantastic job of what science fiction writers often honor more than they practice: writing a story in the voice of someone from the imaginary world of the story, without reference to the contemporary world of the author and reader.
"Night Mail" shows an almost obsessive attention to the details and the feel of Kipling's future world. He even includes appendices of advertisements and official notices from the year 2000. The story also implies huge changes in human society, mentioned in offhand remarks, never explained. (For instance, the narrator accepts reincarnation as a proven scientific fact, and the governments of the world are subordinate to the technocratic Aerial Board of Control.)
J.R.R. Tolkien was similarly obsessive about The Lord of the Rings and the body of poetry and literature he wove around it. We all know how he created entire languages for his dwarves, elves, and human cultures. Apparently Tolkien even went so far as to prepare a facsimile manuscript of the fragmentary chronicle his characters discover in the Mines of Moria -- complete with charred edges and bloodstains. That's immersion.
(I've often thought it's a good thing that H.G. Wells didn't invent roleplaying games when he devised his Little Wars miniatures rules in 1913. If he had, the Inklings would have had an awesome D&D campaign at Oxford in the 1930s, and Tolkien probably would have spent all his time on that instead of writing.)
If Tolkien and Kipling are the pole of immersive imaginary worldbuilding, Lewis and Wells are at the opposite end: fantasy and science fiction written as allegory or polemic, in which the fantastic story serves a particular purpose in the world of the author and reader.
Lewis's Narnia books are explicitly Christian -- although Lewis himself cautioned that they weren't intended as direct allegories. Apparently this difference in priorities was a source of some friction between Tolkien and his friend Lewis. Tolkien objected to Lewis tossing together such disparate elements as fauns and dryads from Classical mythology, dwarfs and giants from northern european legend, and even Father Christmas in the Narnia books. One can imagine him shaking a tense, nerdy fist: "You're doing it wrong!"
Similarly, Wells's science fiction stories always had their
polemical side -- sometimes rather curiously, as in In the Days of the Comet,
where during his description of the humane new world that follows the events of
the novel Wells spends about a page criticizing Victorian interior decoration. No less a personage than Jules Verne criticized Wells for his willingness to bend scientific rules and "play with the net down" for the sake of telling his story.
Significantly, both The Lord of the Rings and Kipling's two future stories are self-contained. The stories are entirely about people within the world of the story. Whereas the Narnia books -- and both Wells's When the Sleeper Wakes and Men Like Gods -- throw contemporary human characters into the fantastic world or the future. The imagined world exists in order to convey a message to people in the author's real world.Tolkien and Kipling are doing worldbuilding for the sake of worldbuilding. Lewis and Wells are constructing stages for morality plays. Note that I am not trying to say one approach is better than the other: certainly all four writers were giants in their fields with tremendous influence even now. But it's possible to trace these two tendencies down through the history of science fiction and fantasy to the present day.