CIRCLE WITH A DOT

@tosbourn

The traditional third in the scifi greats is Arthur C. Clarke. Good Clarke novels include Childhood's End, Earthlight, The City and the Stars, and 2001 A Space Odyssey

@tosbourn

You might want to try a couple of the Heinlein Juveniles. Which despite the name are not just for kids.

https://en.wikipedia.org/wiki/Heinlein_juveniles#Novels_written_for_Scribner's