Sadly, this book didn't stand up to its predecessors (The Dreaming Void, The Temporal Void). Those were pretty good, and this is not substantially worse, but while those were full of interesting ideas and a good balance of SF and fantasy, this one was a little more of a slog.
In the first two books, I found it hard to keep track of the various actors, who was behind them, and who was connected to whom and how. In this book, it was no easier, but I got tired of trying, and just stopped caring. There were simply so many undifferentiated factions that I lost interest in what they wanted. Also, while the first book mentions 'historical' characters, and the second book brings some in, this third book draws on them with a vengeance, leaving me to think that only a fan of Pandora's Star and Judas Unchained ) could really get the full benefit of the book. For me, having not read those, it was simply too much.
Edeard plays an important though lesser part in the book, but I still found his treatment of Salrana not credible, or at least not attractive. Since we're meant to hold him in high regard, that's a significant weak point. The fantasy elements of the book overall were less fun - more political and less convincing than in the first book. They read more as an exercise in careful authorial speculation than as actual narrative.
Hamilton does make a point of tying up loose ends, but he does so with a pretty hefty dose of deus-ex-machina - lots of sages causing unspecified magic to happen, usually while calling on one of those historical figures who just happens to have special powers and still be around.
All in all, it's a decent book, and an acceptable conclusion to the trilogy. I'd still recommend all three books. However, the end is substantially less satisfying than I originally hoped it would be.