I must first have read this soon after it was originally published in 1985. I thought it was a terrific story at the time, and rated it as one of my favourites. I decided to re-read it last week, to see if my view had changed.
The story is set at an unspecified future time in which the Earth has largely been abandoned as a result of wars and environmental catastrophes, leaving the only advanced civilisation living in artificial habitats scattered around the solar system. Most of these are created by scooping out the interiors of asteroids and spinning them to create artificial gravity. As a result of this fragmentation, a wide variety of social and belief systems has become established, with each 'world' having its own distinctive culture (in more ways than one). There is a broad division between the 'Mechanists', who rely on hardware and computing systems, and the 'Shapers', who aim to increase humanity's potential through intensive psychological training and fiddling with biochemistry and genetics. Relationships between these groups are very strained but actual warfare is considered too horrifying to contemplate, not only because of what happened on Earth but also because the habitats are so fragile and easy to destroy. Early in the story, the first aliens visit the solar system – the Investors, who are nomadic traders. Their presence has major consequences for human activities, providing shifting opportunities for some habitats to become wealthy while others fall into decline.
The plot focuses on one man, Abelard Lindsey, who, while brought up in a Mechanist environment, has received Shaper diplomatic training which gives him powerful persuasive abilities. He rebels against the leadership and is expelled, and never really settles again, becoming a 'sundog', or itinerant, moving between the different worlds. He obtains influence with the Investors (via an amusing accident) and becomes a major player in the human habitats as a result. The story stretches over a period of some 70 years, rejuvenation techniques having extended human lifespans. The first four chapters (130 pages) follow an unbroken chronology up to the point of Abelard's meeting with the Investors. After that, the story jumps 20 years and thereafter becomes very episodic, dipping into Abelard's life from time to time (often with long gaps) until the unexpected conclusion.
I was not so impressed with the story this time as I was originally. The long gaps in the narrative broke my involvement with Abelard's story, especially as important things were evidently going on in the gaps (including Abelard getting married and raising a family in one gap, then deciding to abandon his wife to return to his sundog ways during another). Considering that the story is so focused on Abelard (he appears in virtually every scene) his personality is rather opaque and he is not easy to relate to. The main appeal of the novel is not so much in Abelard's story as in its rich descriptions of the future of humanity, covering ecosystems, cultures and politics. In those respects it was trailblazing at the time, and it is still well worth reading.