In one key respect this reminded me of several recent fat SF novels I've read. There's something really interesting and cosmic and mind-blowing going on in the background, but I had to wade through several hundred pages of murky plotting, interminable and impenetrable technobabble and unpleasant, poorly differentiated characters to get to it. The parts I was really interested in were one key flashback near the beginning, and the climax and epilogue. A Golden Age pulp writer would have just given us those parts and brought it in under 150 pages, without losing any of the epic scale.
When we finally get to the meat of the story it's pretty impressive and evokes a genuine sense of wonder, although sometimes it feels like Reynolds has over-egged the pudding by piling on too many revelations and reversals in the last couple of chapters.
Worthwhile overall, but I don't think I'll bother with the other two in the series.