"Childhood's End" is one of the best novels of the 20th century. Arthur C. Clarke is one of the best writers of the period.
Many scenes from this book have been cribbed into the public consensuses over the years via Hollywood movies, some good and some bad. The most specific image copied from it is that of the giant space ship hovering over cities... done so whacked out well in the movie "Independence Day". Of course, there the aliens were evil invaders rather than the benevolent Overlords. Other ideas that morphed from this novel into Hollywood flicks were in the films 2001 and 2010. Of course, Clarke was directly involved with both of those, so they were much more faithful to the source materials. And naturally, Clarke's influences are seen in Star Trek, Star Wars, Babylon 5 and other Hollywood SF series over the years.
The major question dealt with here is "where are we going?" as a species. The weirdness is that many people don't like the answer Clarke attempts to give here. I, myself, don't find it an appealing concept. I am not sure what I don't like about it other than that it seems Alien to me. Very alien. Which is why this is great SF... Clarke makes us feel that we humans can be aliens to ourselves, and not in a normal way. It is something that I think Asimov himself hooked into with his later Foundation novels and the Gaia concept... but Clarke did it first.
Clarke, along with other writers like Isaac Asimov, Robert Heinlein, Philip K. Dick, Theodore Sturgeon, Fredrik Pohl, Ray Bradbury, Harlan Ellison, and several others, made the future what, in many ways, it has become.
Clarke has written many other novels on, somewhat, the same concepts... "2001:A Space Odyssey", "Rendezvous with Rama" and "The City and the Stars" standing out, with this novel, as, in my opinion, his best work. Read this book for something that is more mature in outlook than the usual Hollywood faire that gets the sci-fi label.