This book is the second of a pair. The first was The Quiet War. See its reviews for the background to this one.
After the Quiet War, many of the Outers are rounded up into prison camps. The ones that escape capture, the Free Outers, flee to Miranda, a moon of Uranus, to recover and rebuild. They are forced to flee again to Triton, a moon of Neptune, after Greater Brazil sends ships after them. Again they are moved on, this time by Ghosts, fellow Outers who follow a reclusive leader who in turn follows orders from a future version of himself, who is supposedly on an extra-Solar planet. Orbiting remote Nephele, the Free Outers, now wary of permanent habitats, build the "Gardens of the Sun", detached bubble habitats that are closed eco-systems drawing extra energy from the Sun.
The Gardens of the Sun are but one of many types of long-term closed habitats, ranging from the many scattered emergency self-regenerating survival cabins Outers need in case of suit or major habitat failure to the artistic creations of the Outer 'gene wizard' Avernus, who delights in creating hidden 'gardens', each one following a completely different design in its combinations of 'tweaked' living organisms, based on archetypal animal and plant patterns. A more utilitarian approach is taken by Sri Hong-Owen, who creates 'cut' humans for various purposes, not all pleasant. Both women come to very different ends which signal how their approaches differ.
The Outers draw their strength as a community of individuals working together. The three Earth blocs against them, united under the banner of the Three Powers Alliance, soon start squabbling over the spoils of war. Earth's bloc governments are very much like many of Earth's national governments now: dictatorial, controlled by cliques, using a veneer of democracy. These governments use their own people, and there are some poignant moments for a spy and a war hero who discover the truth about their engineered roles and rebel. While things change on Earth, it appears a spent force, woefully contradicted by greed for, and Green zeal against, wealth and power. In contrast Outer society is very much idealised (apart from the cultist Ghosts). Even in defeat, these individualists never give up. Living a seal away from a killing vacuum presumably breeds discipline and endeavour.
While there is no FTL drive in sight, and robots are just clever, but not intelligent, workers, this novel re-invents optimism in space exploration. It sidesteps the dead end of building another Earth by terraforming Mars, and instead proposes a new goal of colonisation of the entire solar system, and hints at a new type of 'generation starship', built around Outer closed eco-system designs.