Clear as Water in a Transparent Solid State (or Ice)
The world of Childhood's End had some pretty heavy subject matter to get across to the reader—science, alien technologies, paranormal activities, extraterrestrial landscapes, and the transcendence of the entire human race to name just a few. Just listing all of that produces a terrifying combination of syllables.
But there's nothing to worry about here because the writing style Clarke employs in this novel makes dense subjects super accessible. Check it:
Out of the orifice, a wide, glittering gangway extruded itself and drove purposefully towards the ground. It seemed a solid sheet of metal with handrails along either side. There were no steps; it was a steep and smooth as a toboggan slide and, one would have thought, equally impossible to ascend or descend in any ordinary manner. (5.9)
Here, Clarke is describing alien technology unlike anything we have on Earth outside of some super-secret government facility or maybe Google headquarters. But the language is so clear that we never lose track of the image. The sentences are never overly long and complex; they just flow into each other. And Clarke uses accessible images to help us along, such as "smooth as a toboggan slide." We don't know alien tech, but we do know about sledding.
Clarke manages to keep this clear, precise style going throughout the novel, even when dealing with such oddities as Jeff's space-faring dreams or the Overmind. So while the subject matter may get heavy from time to time, the style never adds any extra weight to the reading.