The time - a year or more after Star Wars, certainly from the time when "Wow, Star Wars is big, what SF stories do we have?". I believe, but am not %100 certain on this that it had proudly emblazoned on the cover "From the publishers of Star Wars" (I may be conflating this with "Damnation Alley", which definitely did have this.
It was a fairly pulpy tale that involved political exiles from some alien planet being exiled to earth via some kind of stargate thingy (?) (earth of I guess the 60s or 70s).
They were human appearance, but I remember as being very tall?
There was possibly some back and forth stuff with the home planet, but I remember nothing else, except the cover was a character wielding something that was not exactly unlike a light-saber. Which was totally misleading, but the whole packaging screamed of "SF is big now, this is a SF book".
It's quite possible that it's by a well-known author, but I've not been able to remember anything else about it.