In the tradition of "Brave New World" and "1984," this novel is about our own society in a fictional, not too distant future, shaped by political and technological trends discernable today. The plot hinges on how we might react when confronted by an alien society that evolved on an Earth-like planet, going on to travel and live among the stars for millions of years. These could be the UFO people of Roswell, or of other UFO sightings such as one the author experienced. In this novel the aliens have had an "anthropological study" outpost in our solar system for the past twenty-five thousand years, watching, tracking our progress, and waiting to see what we will make of ourselves.
The action begins nine years after human discovery of this outpost has emerged to the public. The story's human characters live in Uspa, a country long accustomed to exercising dominant military and economic power. While its intelligence services have learned the aliens are essentially non-military, the country's leadership is dismayed because advanced alien technology is being licensed to Uspa's geo-economic rivals. Clearly if this goes on it will undercut the intellectual property system that undergirds Uspa's economic primacy. This sets the stage for the central dynamic of the story: an attempt to drive the aliens from the solar system.
Part of Uspa's strategy involves capturing the space-habitat project that's been under construction by the aliens, using volunteer human labor. Once secured, this would give Uspa a trove of alien technology. Also, it is perfectly situated to be a base station for mineral prospecting and exploitation of the asteroid belt. The arc of the story takes the key characters out to this unfinished habitat project, and then on to the alien's observation station "counterplanet", which is a much larger habitat, and then finally back to Earth for the resolution. A central character on the human side of the story is the special-operations officer who has the job of capturing the unfinished space habitat. The pilot he hires and that pilot's girlfriend, who hates the idea that her lover is mixed up in such a zenophobic plan, fill out a comedy sub-plot.
The aliens in the story are characterized as fully as human characters. Because they have been traveling in space for such a long time, the zini -- this galactic civilization's original spacefaring species -- has found and made common cause with a number of other sapient species. The poetic hero of the story is from one of those auxiliary species; he is a non-technological bird. An equally important role is played by a female from a second non-technological species; we track her personal life as she meets and mates up with a male of her species who plays another key role.
Unlike much contemporary SF, the "science" in Friendly Invasion is intended to be reasonably realistic. However, some aspects that would be plausible to scientists are so arcane that readers might think it's fantasy. To correct any such impression you may wish to consult this -- Science or Fantasy ? -- companion page when such doubts arise.