If your novel is not set on Earth, you need to devote some effort to world-building. Probably a lot of effort. The stock world of fantasy is, of course, Medieval Europe, but these days stories that use that setting feel a little tired. Readers in North America and Europe will relate well to that sort of world, and it’s nice to give your readers something they can relate to. But if you want your book to stand out from the crowd, giving it some unusual characteristics will help. Recent fantasy settings sometimes borrow from Africa, India, or pre-modern China, all of which are less hackneyed.
World-building is a rabbit-hole. You can tumble down it and never come out (though while wandering around down there you might observe a baby turning into a pig or a dormouse asleep in a teapot, or even have a chance to play croquet using a flamingo for a mallet). Indeed, many authors don’t bother. Science fiction is full of books with desert worlds, glacier worlds, grassland worlds, and so forth. The authors of these books cheerfully ignore the fact that the only world we know anything about has quite a variety of habitats — and for reasons that are not hard to discern, having to do with the amount of heat that arrives in the form of sunlight at different latitudes, to say nothing of global air circulation patterns, which dramatically affect rainfall patterns.
So far I’ve had no luck shopping my most recent novel. Submissions (last month) to 28 agents have given me a dozen rejections, and I’m sure more are on the way. I’m convinced the story is good, but I’ve also begun to see that my fantasy world is rather thinly imagined. Maybe I need to do another rewrite and beef it up.
There’s a danger in this impulse, however. Some writers — mainly (though not exclusively) aspiring authors of dreadful self-published fantasy — are so enamored of their world-building that the story can grind to a halt for many pages while the author regales the yawning reader with the long and turbulent history of the empire, the physics that allow the faster-than-light spaceship engines to work, or whatever.
If the world-building doesn’t genuinely contribute to the story, a little goes a long way. Toss in some vine-covered ruins, have somebody exclaim, “Oh, that was a fine castle during the Pysnikka Empire,” and let it go at that.
On the other hand, careful world-building may suggest story details that you wouldn’t have thought of otherwise. In my new novel the lead character finds herself being betrothed to a young man she has never met. (It’s even more complicated than that, but no spoilers.) If I were doing a better job of world-building, I might ask myself how betrothal works in her culture, and why. Is it an obsolete custom, or is it still actively practiced? Is it found exclusively among the upper classes, or do poor parents also betroth their daughters for money or prestige, or perhaps out of fear? What are the penalties when a betrothal is broken? The answers to these questions all potentially contribute to my plot. I really ought to ponder them a bit more thoroughly.
World-building isn’t just about culture and geography. It’s also about emotional tone. Modern fantasy readers seem to like a darker, more emotionally fraught tone. You could do an amazing job of world-building, but if your story is set in a sunlit utopia, the reader reaction may be, “Meh.” Stir in a gallon of gloom and your sales are likely to rise. Personally, I burn out on gloom pretty quickly, but I’m not a typical reader. I kind of like playing croquet with a flamingo, actually.