My review - recycled from Goodreads:
Why do bad things happen? Are wars and genocide the product of the actions of a few hyper-evil people?
Pohl’s answer in this novel is that major historical events are not caused by single figures of great virtue or great evil, but rather by the small actions of everyday people due to impulse, greed, and misunderstanding, with a large dose of chance.
Pohl heaps scorn on the “brinkmanship” philosophy which argued that one can rely on one’s opponents to recognize that your actions take things too close to the brink of disaster, and thus that their only reasonable response to to acquiesce to your demands - in the world of Jem, this approach is tried by all sides, and rapidly leads to disaster.
Pohl underscores this theme with persistent use of irony; characters misunderstand the actions of others, and their own motivations in ways that are clear to the reader but never become clear to the characters, with the final chapter giving a look at the kind of society the survivors have created - one that those at the top of the hierarchy can describe as being free of coercion and devoted to peace, but which the readers will recognize as practicing slavery and expansionist policies (and yet, Pohl seems to be saying that the self-serving lies of this society are no worse than those of our society).
It’s not a “feel-good” book - but it is a powerful one, with at least one moment when some of the characters attempt to break free of the path that they have been led down, to do something good instead; if more had done so, earlier, the world of “Jem” would have been a better one - and I think Pohl intends the same lesson to apply to our world.