The primary reason that Hollywood has, so far, left the book alone, is likely that it’s very much a novel of ideas. Now, that term doesn’t have a single, commonly-agreed-upon definition, so let me give you mine.
All novels have a throughline that guides the reader from beginning to end, an element central to the book. Traditionally, that’s a main character or a set of several main characters whose actions progress the plot. The more complex the novel, the more complicated the main characters and the bigger their symbolic significance. Believable character development and an organic, cohesive storyline are believed to be the marks of a good novel.
Childhood’s End doesn’t fit this. It’s a work that’s remarkably unconcerned with even establishing a main character. There are a handful of returning characters, to be sure, but they’re almost incidental. The very structure of the book, with numerous quite long jumps forward in time, prohibits us from following them from start fo finish. The leader of the UN, who seems to be set up as the protagonist, is only around for the first couple of chapters, for example; the only character who’s even in the entire novel is one of the aliens.
Instead, the novel is interested in a question: “What is the cosmic purpose of man?” In the book, Clarke invites us to observe one answer to that question. That’s the throughline much more than the characters. There is no plot to speak of, only snippets, scattered episodes. These vignettes don’t really add up to anything thematically or story-wise; Childhood’s End is not an episodic novel with a masterful synthesis at the very end. Their purpose is to show the reader what might happen if giant spaceships started appearing over Earth’s cities, with powerful and mysterious aliens forcing humanity to grow up. Hence why I’m calling it a novel of ideas: the characters don’t need to be more than ciphers because we’re not really meant to identify with them. They’re like lab rats in an experiment, Clarke is the scientist who’s set up the environment, and we’re visitors watching the results.
As a result, the novel’s mood is rather clinical. That’s not to say that it’s boring, far from it, but tension is derived not from fearing for the fates of individual characters, but from wondering how it is all going to end (“it” being the chain of events set in motion by advanced aliens taking humanity under their wing). The selling point is the idea, not a thrilling plot. The characters, for the most part, are very reactive and don’t have a whole lot of agency (and even where they do, there’s no such thing as an action sequence or a heroic stand against evil). And that’s probably a bit too non-traditional for at least a mainstream movie. Hollywood might try to streamline the story by condensing the timeline and creating new action scenes for a main character to play hero in, both of which would run counter to what Clarke is trying to say: in his scenario, change takes time, and we humans don’t – and can’t – do a lot to stop it.
I can’t really say anything more without spoiling the novel’s big reveals, which I don’t want to do. Let me say only that despite the lack of relatable characters or a driving plot, I was never bored by Childhood’s End. Its vision of a potential future is intriguing enough on its own, and I’m certain that the ending, which is hopeful and bleak and final and open-ended and mystical and down-to-Earth, all at the same time, is going to stick with me for a long time.