A lost interstellar expedition from long ago returns to find their original home planet ("Minerva") destroyed, and a new, unknown race--us-exploring the Solar System and about to expand into it.
I had long been skeptical of stories about invasions by hostile aliens. It seemed to me that any civilization able to travel between stars would have solved the kinds of problems that humans who believe resources are finite fight wars over. So these aliens were benign. But not just because they had overcome primitive aggressive traits, or because the author decided arbitrarily to make them that way. The Ganymeans are inherently nonaggressive for reasons that go back to their evolutionary background and biological ancestry, and a large part of the book deals with their grappling to come to terms with the very different nature of humans, and the violent history that it has resulted in.
I've never found UFO lore convincing. Too much of it consists of contrived explanations to explain away the lack of hard evidence. It has always seemed to me that if we ever do make contact with an advanced, star-faring culture, we'll know. There won't be any doubt about it.
See Dr. Attila Torkos' Giants Chronology for a timeline, recently updated to include all five novels. Click here to view the HTML version on-line, or right-click here to download an Adobe Acrobat PDF file, nicely formatted for printing.
This novel is also included in:
The Minervan Experiment
The Giants Novels
The Two Moons