I dunno, I expected more oomph of a penultimate book. Tension-wise this series has been cruising along at about 3-out-of-10 for the last couple of books, and now the author has ratcheted it up to a 5.
This is not to say nothing happens -- stuff happens; but it's not strikingly apocalyptic. Jack goes after the evil mastermind Rasalom, guns a-blazing. Spoiler alert: Rasalom survives this. Then Rasalom begins his final plan of evil conquest, with Jack and the gang racing to cut him off at metaphorical pass. I won't spoil that, but there's a sequel called Nightworld, so take a guess.
Rasalom's plan is kind of dumb, it turns out. I don't want to complain too much, because the story moves along and there's some twists and some deaths and some seriously creepy stuff, but I got to the end and thought "That was it? That was the whole plan? But then why did he bother doing and and..." I think there was a peak several books ago, when the bad guys were melting holes in New Jersey and entombing human sacrifices in cursed concrete columns and it all seemed like fragments of a vast plan of evil conquest. Since then, Wilson has been trying to unify his mythology (e.g., the importance of the Lady) and it just doesn't work as well that way.
However: the creepy bits demonstrate that Wilson can still bring the creepy, so Nightworld should be satisfying in that way, at least. And if not, hey, the series will be done and I can stop complaining regardless.