This is a fine book about a future world in which multiple virtual realities exist alongside 'atomic' reality and a human being may choose to have multiple versions of themselves made (and where illegal copies of human beings may be made for the purpose of abuse and exploitation). The world is ruled by AIs who seem benign but may not be. Hyper-intelligent robots co-exist alongside human beings: strange subtle, devious, passionate robots, very much against the grain of what we expect robots to be like. Human and artificial intelligence alike face a strange new existential threat from beyond the galaxy.
Like its predecessor Recursion, this is a subtle, ambiguous book which really is about life, the universe and everything. It's full of thought-provoking ideas and not only ideas about only about robots and artificial intelligence (though Ballantyne clearly knows what he is talking about here) but about belief and certainty, good and evil, free will and determinism, childishness and maturity...
There are some great set pieces: the scene in the cave on Gateway, the showdown between Judy, Frances and Chris... At times it is nightmarish, at times absurd, at times touching and hopeful. Like all the best imagined worlds - and like the real world - there isn't a tidy edge to this fictional universe. It extends beyond the horizon. You could reread the book and find new things in it, or change your mind about what is really going on.
Highly recommended. I look forward to the third novel.