Funny what you remember. Almost all I could recall about this one was the monstrous figure of the Archimandrite Luseferous: a hellish tyrant of the worst sort imaginable. As the narration describes him: “that most deplorable of beings, a psychopathic sadist with a fertile imagination.”
And I remembered it was about gas giants, and wormholes. And an important Secret. I remembered the Secret. Oh, and of course the fact that — in a massive difference from the Culture novels — it describes a galactic civilisation which proscribes AIs; mercilessly hunts down and destroys any hint of machines gaining sentience.
But not really anything else to speak of. So it was really great to read it again.
Highly recommended if you haven’t read it before. Or even if you have.