Gilpin’s Space by Reginald Bretnor

The Kremlin and the conglomerates were tightening their grip. The Individualist People’s Party was allowing every individual to be exactly like every other individual. Then Saul Gilpin discovered a new kind of space and disappeared into it with a stolen submarine.
From the gray malevolence of Earth, he had broken through an incredible gateway: to the far, wondrous reaches of the universe–and the one last chance for humankind to forge a new beginning.

Now his friends will follow, if they dare. They will flee Earth, for a bold journey through…

Gilpin’s Space.