Egan is very original and his novels are definitely "hard sci-fi" in that they make you think.

However, I regard him as a bad writer, as his dialogue is very bad, his characters hollow and his plot progression is rather jumpy.

Read him for his stimulating ideas, but not the way he tells the story.

His Permutation City is also good.

Permutation City is probably the best hard sci-fi novel I've ever read.

There was some page towards the end I remember being hopelessly lost and never recovered.

You mean yourself or the plot? I think that in the third act Egan added some weaker elements both as a corollary of the idea being explored and as a way of introducing some traditional action, in a novel that is otherwise mostly the setup of an elaborate thought experiment.

Nonetheless, I think the result is extraordinary, because the problems posed, the paradoxes highlighted, and some brilliant insights, are new and valid outside the fictional world created in the novel.