Archipelago is set in a distant future. The stars systems within a few hundred light years of an origin planet have been colonised via a network of wormhole-style gateways, put into place using relativistic journeys between stars systems. The colonisation has been long and complicated with vast dendritic networks of planets and systems forming. Distances are temporally vast and yet practically tiny due to the existence of the gateways: coupled devices that tunnel through spacetime.
A complex civilization has developed across the star systems. The centuries of colonisation have created profoundly different peoples, cultures, languages and political systems. Much of this is tense with political intrigue. From this chaos have emerged great leagues/guilds of planets, each unified by some combination of ideology, convenience, trade or history. Some are highly interconnected, making for a highly homogeneous culture, and others, more loosely connected, have more diverse cultures.
Two technologies have enabled this advancement. The most important of these is gateways, which have allowed easy movement between stars and planets, along with long distances on planets. The second is AI-driven self-constructing builders, tunnellers and terraformers. These can mine, manufacture and, through armies of vast self-replicating machines, turn barren rocks into habitats and planets.
As new star systems are reached, few present prospects for colonisation, but some have rocky worlds that can be turned into 'habitats', a life interior of caves and tunnels. Very occasionally planets are discovered with an atmosphere that can be converted to something breathable and fit for life. Then the machines move in and over centuries new planets emerge.
Just finished Archipelago and wanted to say how much I enjoyed both the story and writing. An elegance and gentle beauty I've not found in sci-fi for a long time.
Thanks.