Nutshell: antisocial nerd, responsible for historical amendments to spacetime continuum, dicks it up for everyone in order to lose virginity.Eternity
is an interdimensional NGO, set up in the 27th century (32), initially to carry on intertemporal trade (43), which trade was promoted as its primary purpose. Its true primary task is to "prevent catastrophe from striking mankind" and "to breed out of Reality any factors that might lead to such knowledge" of its biotemporal management of human history (43-44).
We see that the main component of biotemporal management is actually wealth management for each century: "The Sociologists had an equation for the phenomenon" of uneven wealth distribution (45). Biotemporal managers allowed aristocracies to form, so long as they "did not entirely forget their responsibilities while enjoying their privileges" (46). Analogues to marxism here to the extent that the managers viewed the aristocracy as a ruling entity, "a class, not as individuals" (38). Generally, the point is to protect the species from destroying itself in nuclear war, but there's talk in the NGO of abolishing space travel, which always turns out to be a disaster.
Some odd gender politics: no women in the NGO, for the bizarre reason that removing females from the spacetime continuum actually has a more deleterious effect than removing males (something to do with the birthrate). Plenty of commentary, express and implied, on freedom & determinism. Strikes me that determinism is the default position when the premise of the story is that changes initiated by the managers at one point alter later effects. That said, some characters believe in "temporal inertia" (169), and that effects from changes return to a hypothetical baseline after a nunber of centuries, rather than creating further diremptions.
Anyway, lotsa paradoxes, including the central paradox of the novel (or, rather, of the Setting, rather than the Story): how is it that changes to history do not effect the NGO when the NGO interacts with and draws from history?
Nifty link toward the end to the Robot/Empire/Foundation setting: safe to say that the denouement is the condition of possibility for that narrative.
Recommended for those who stumble upon temporal field theory without being aware of its mathematical justification, persons for whom human appetites carry a quivery repulsion, and readers who associate the mushroom cloud with the system by which private capital was invested in business.