Miéville is freakishly skilled at using outlandish world building to good effect.
The City and The City, Perdido Street Station, and Kraken all showcase his talent, and I think the common thread among those three really outlines what’s essential to his take on world building that’s narratively useful.
All three of those novels have a core conceit that’s essential to the plot that you’d call world building, but more than that they’re all set by and large in the context of a built environment: they happen in cities. Beszel and Ul Qoma, New Corbazon, and the unseen margins of London respectively.
Cities are quite literally “built worlds,” and people who enjoy them can tell you about the energy, and the sense of history submerged just under the surface of any given space. They’re both lived in, and vibrant and alive.While the layout of a city may seem accidental, it’s actually an aggregate of many different intentions, and that means earlier stories. And I think the best world building tries to establish that same sense for people who will interact with the media.
A good setting establishes a sense of place, and provides a story with context. I think that this is because any real-world story will have these things as well. Where you are when a story happens, usually matters. And why that location matters is the result of a whole other set of narratives. For a fourth Miéville example, look at October, his history of the Russian Revolution. Palaces, train stations, bridges, and apartments are all both set dressing, and influential aspects of the setting.
However, it’s important for that world building to weigh only as much as is needed to improve a scene or impart information. If it gets in the way of the plot, or does not tell a sufficiently interesting story on its own, it needs trimming.