The protagonist is originally from Mars, where he grew to adulthood before emigrating to Triton, one of the moons of Neptune. There is a war going on between Neptune and Earth. Mars and the smaller satellite colonies like Triton are technically neutral but everyone knows it's just a matter of time before they get dragged in, especially after the city momentarily loses gravity as a by-product of a battle between the planets.
Life on the satellites is much more anarchic and loose than on planets like Earth and Mars. Like most of the citizens of Triton, Bron lives in a co-op. These are communal dwellings organized either by gender, sexual orientation, family unit, political leanings, or a myriad combinations thereof. Although this set up means that almost anyone can find a suitable group that fits their inclinations, Bron feels vaguely unhappy and unable to fit in. He is single and has no close friends, but does get along with his his roommates; he plays complex wargames with the elderly Lawrence, enjoys mentoring young Alfred, and enjoys a complicated mix of admiration and jealousy with Sam, a diplomat.
One day he meets Spike, a performer with a traveling troupe of street artists. She involves him in an impromptu piece of street theatre and he becomes obsessed with her. He manages to find out her troupe is on Triton for a brief period and has a short affair with her before the group leaves on tour.
Sam is dispatched to Earth on a government mission as tensions escalate, and he invites Bron along. When they get to Earth, Bron is arrested without charges and briefly tortured. Sam gets him out but tells him he can't tell anyone in case it causes a scandal, and the two travel to Mongolia to stay out of official sight for a bit. Bron is unsettled by the experience but thrilled when he finds out that Spike's troupe is also in Mongolia. He finds her and tries to renew their relationship by taking her out to dinner, but finds himself even more out of place than on Triton and the evening ends badly.
He and Sam return to Triton and when he lands he finds a message from Spike for him telling him that she doesn't wish to speak to him again. Bron is angry, but has no time to deal with it since moments after the landing the city is attacked. The shields fail and damages are massive, and when he gets home he finds the co-op in shambles and Alfred dead. He and Lawrence try to evacuate, but can't get very far due to collapses. They end up helping a neighboring co-op for a bit, which Bron takes great pride in.
When the dust eventually settles, he finds out this was the last battle in the war. Mars was also hit, and the retaliatory attack on Earth was devastating, killing two thirds of the planet's population and ending hostilities for good.
In the aftermath of all this, Bron is still adrift and obsessed with Spike. He decides that in order to finally be happy, he needs to change everything about himself.
Best part of story, including ending:
The society on Triton is interesting, clearly modeled on the 1960's and 1970's commune type experiments but on a grander scale.
Best scene in story:
The attack on Triton when the shields fail is very dramatic and scary, and believably high stakes.
Opinion about the main character:
Bron is very self-centered, he's meant to contrast with the utopian set up where everyone can find their bliss, but as the world around him goes through horrible changes you get increasingly frustrated with his navel gazing and self-justifications for bad behaviour.