Childhood's End is still in print here, at least; a trade pb through Random House. And my point about the later
Dune books was that, by being best-sellers, they got people to go back and look at the original, simply adding to the level of interest in it. So I'd say there's a lot to support the idea it would still be in print even had a film not been made of it; as genre fiction tends to have many things that stay in print for decades, without the least input by Hollywood.
(This is not to deny that films do sometimes help; but for Hollywood to set trends in literature is seldom a good thing, as it often leads to the debasing of literature into, as I said, "bubble-gum", throwaway reading matter, instead of something that is of higher quality -- which also does
not imply not entertaining; high-quality writing can be entertaining, but it offers more than
just entertainment.)
(Lord, I hate having to add so many qualifiers to my sentences just to get the point across....!
)