E.C. Tubb 
Starslave [EPUB ebook] 

On several settled worlds of the Earth Confederation, towns had been utterly destroyed by attacking alien vessels — exploded into flaming ruin, and fleeing people reduced to smears of blood and bone. And so they sent for Captain Kurt Varl, the only man to have fought an alien ship and destroyed it — the only survivor from his crew of thirty souls. And now he would have to lead another ship and crew into battle, knowing that as well as the alien raiders he faced the things that lurked in limbo, existing in four dimensions and capable of transforming humans into things of screaming horror…