Paperback: 224 pages
Publisher: Bantam Books (Mm) (Nov 1985)
Originally published in 1978, this is good old fashioned SF of the 'take a premise and run with it' form. In this case, it's that a new stardrive, when used at full power, causes the ship using it to slowly drift between alternate universes.
Here, there are 4 stories. The first is very much that of what happens when the first ship arrives back at Earth, to find that although almost everything is the same, there are differences. The second, third and fourth follow a couple who decide that, so long as they have each other, they're perfectly willing to be couriers, together taking a small courier ship from Earth out to the colonies and back again, and never mind that the source and destination are never in the same universe.
As an ideas setup, it works well. And the characterisation shows up well, too - despite the premise being one that could have come from the '50s, the genders have reached equality with Raelle being an equal partner to her husband Jay.
Good, traditional '70s SF.