The Star Dwellers by James Blish is one of two linked juveniles he wrote. Neither is a really good book, but they have their interesting points.
Jack Loftus is a cadet for the Secretary of Space Daniel Hart. The current crisis involves the violent discovery of The Angels, beings living in the Coal Sack Nebula that are not life as we know it. They are apparently similar to ball lightning in appearance, but very old, and very powerful beings.
So Jack, trouble-shooter Dr. Langer and his cadet Sandbag Stevens go off to visit them to conduct treaty negotiations.
Blish was apparently working out some political agenda in these books for the society he has set up is rather different. It seems to me to be somewhat elitist in ways similar to the Lensmen novels of E. E. “Doc” Smith. You can’t vote unless you are employed, and many people are not allowed to have children since they are not intelligent enough.
I am aware of the problems that other authors have pointed out in this area. It does seem as if the smart and ‘successful’ people of the world do not have many children, while the poor do. See The Marching Morons by Kornbluth for example.
But this society seems vaguely fascist to me . I am very in favor of the rights of individuals and this society seems to have trampled on them a bit too much.
But the story is pretty good, there is a lot of action, and the Angel are an interesting alien life form. I wish he had spent more time developing and describing them, rather than the society on Earth.
All in all a reasonably good book.