Let's get the bad stuff out the way first of all...
This book is too long, by a country mile. It is a good 200 pages longer than its prequels, which were themselves too long as well. And it really feels it... it seems to take an age to move that old Kindle percent-o-meter. So the first thing to say is that it really needs a good editing - I can't help but think that all of the Jed/Gerald arc could go and the book wouldn't suffer for it.
But that's not the end of its problems.
It also lacks a lot of the intensity of book 1, with the possessed becoming shadows of their former selves. Gone are the unstoppable psychopathic juggernauts. In their place are foes altogether less nightmarish. This robs the book of the horror element from earlier...
It lacks scale... at one point, over the course of 100 pages or so, the main characters undertake a voyage beyond where humanity has every traveled before. But it doesn't feel like that. There's no sense of distance or time or effort. There's a rushed encounter with a new species that has absolutely no nuance or intrigue to it at all...
The cast is way too big, with very few memorable characters. Too many identical gangsters, too many ships, too many planets...
But for all that, it does have redeeming features. I loved the Mortonridge stuff (though the resolution was a bit... sudden). I enjoyed the attack on Trafalgar. I even liked the scenes in the refuge continuum, with the efforts to stave off that dimensions dark denizens...
And then we come to the ending...
It's fair to say that the resolution to this 3000+ page story is a bit of a deus ex machina, both literally and metaphorically. It is all sorted out by a wish that everything was better, and then it is. It's vaguely interesting how it is justified or what it aims to accomplish, but it feels sudden and unearned. Almost like the author desperately wanted to finish this lengthy work and just... did. Still, it's hard to know how you would tie up all those endless plots in a satisfactory way...
So you may be wondering why I give this four stars? Well, for all its many, many flaws, it is still very readable. It trucks on at a fair old pace, never really hanging around on much for long. So it never feels slow, despite the length. It also still has some good ideas and some interesting tech. And there is a small amount of satisfaction from watching Joshua resolve the situation with a click of his fingers... kind of like a power-trip fantasy.
I just wish it was a bit less.... long.
