The third and last book in Egan's Orthogonal trilogy, The Arrows of Time sees tensions mounting aboard the generation ship the Peerless (again), as a new messaging system is devised which can bring news from the future. A large minority of those aboard feel for one reason or another that this is a Bad Thing: that their freedom of choice has been taken away and their paths mapped out unalterably. When the disagreement begins to evolve into violence, a small crew is sent out to a distant planet to find out if it's inhabitable, with the idea that the so-called anti-messagers might be moved there to save the ship from destruction.
It's a book about free will, and it reveals the overall theme of the trilogy: the right of a sentient being (the characters of Egan's trilogy aren't human) to translate their will into action, a right which Egan sees as facilitated by science and by doing science.
I actually found it quite boring. The feminist issues which gave the first two books such contextual urgency are markedly absent, replaced by a sort of vague discussion of the default Issue of the moment, terrorism, a discussion undermined by the fact that the saboteurs preparing to bomb the messaging system are so unequivocally in the wrong (Egan makes it clear that they're using much more explosive than is actually needed to take out the system). It's also not resolved particularly helpfully: male and female become, by the end of the book, folded into one; there's no attempt to, e.g., work out everyone's differences among themselves.
The lack of plot interest also means that the physics sections become that much more interminable; I suppose it would be possible just to skim them, but unfortunately I'm one of those readers who has to read every word, thoroughly.
A disappointing end to the series. I'm still unconvinced that this actually needed to be a series: The Clockwork Rocket was a fantastic book which would have stood perfectly well on its own.