I read this right after finishing The Stress of Her Regard, and liked it even less. If the rules for dealing with the prehistoric vampiric entities, which are at various times stony and dragon-like were unclear and seemed a bit arbitrary before, they were really puzzling here. The activity and images were so bizarre that even Powers' powers of description weren't adequate some of the time. There was memorable and creative imagery - I'll give it that - but when you don't know what the ground rules are it's hard to decide whether something is terrifying, weird, or even normal.
But I will say that it had some of the most memorable images I have ever read. I have to give it that.