He also goes by Sir Author Charles Clarke, different.
That is cool!  Not something I was aware of.  I think I liked his novella Childhood's End the best.
That's the one where there is robotic overlords?
No.  Its the one with benevolent aliens that are helping mankind.  But, the never describe what they look like until the very end.
What did they look like?
That would be cheating to tell you... It turns out that in the ancient past they had visited the Earth, but had messed up the first contact.  The came back century's later.
Ah ok. He lived a long life of 90 so he got to tell us many stories at least.
Actually, you were right.  I think they were known as the overlords.  Just not robotic. Yes he was a prolific writer. A lot of classic science fiction.
What else did you enjoy?
I liked his Rama series as well.