World Swappers is an early work by Brunner. It is short and dense in the same way a lot of books written in the forties or the fifties tend to be. It has several threads, and a fast pace but does not leave you behind.
I will say that the characters do sometimes lack depth, it is definitely an early work, none the less it is a good book that I have re-read a couple times over the years.
The book is set several centuries past us developed the first FTL ships, and when dozens of worlds were colonized.
It’s about two people/organizations who are both trying to solve the same problem, even if one does not realize it.
The first is Bassett, a business man who under normal conditions would be the top guy on earth after he puts in his time (a few more decades) he could then spend the latter half of his life as the de-facto ruler.
The second is Counce, centuries before the book started, just as humans were going in the stars, he discovered how to build the Transfax by accident. The Transfax is a teleporter then can go between stars, and can even change matter to other forms. It could end hunger, and disease, providing anything anyone ever wanted for practically nothing.
However he realized quickly after he build the first one that it could also end mankind, even in theory you could not shield from someone sending a bomb to you via Transfax. So long as you know where your enemy was you could kill him, and once the Transfax was out you could easily make more of them. To let everyone have it could mean the end of mankind, to let no one have it would be a breach of his duty to his fellow man.
He decided to compromise. He founded an organization, selecting the best people he could find to use the Transfax to help in what ways they could without revealing that it exists. They could play the long game because they could use it to come back from death and to reverse old age. They also used psychological modeling to make sure they got no bad eggs.
It is a very interesting book, partly because it has such a optimistic view of mankind via Counce and his people. Yet on the other side you have Basset and other such horrible people. It shows that a book does not need to be wholly optimistic or pessimistic, it can be both.