Once the adventure gets going, I got caught back up in it. It's quite fun, involving a cowardly magician who is on the run and a nefarious Dutch industrialist who is doing sneaky things with companies (whose ruin impacted one of Sally's clients which is how she started to sniff around). Unfortunately, I found the ending very frustrating on two points. One, which is spoiler free, is that it feels brief and truncated compared to all the investigating and plotlines that came before. You kind of figure it out quickly and the bad guy gets dispatched all too quickly. Pullman was trying, I believe, to make a modern retelling of the Victorian penny dreadful. He does a great job of setting up the environment and the story and then elevating it with modern sensibility. However, he spends most of his energy on bad stuff happening to the characters (which is fine), but doesn't give the reader the satisfying payoff of the ending.
I remember when I was teaching and the His Dark Materials was all the rage among the middle school kids. The last book actually came out in 2000 and the kids had been waiting for it. I personally read it and quite enjoyed it, though I do remember feeling it ended with a bit of a whimper rather than a bang. But the kids hated it! They were so mad about the ending that it ruined the series for many of them. I kind of get where they are coming from now. I was reading it more as a critique of Christianity and I enjoyed that, but they were focused on the relationship between the two main characters and he did totally pull the rug out in that one. I kind of think he is trying to be too clever and he showed signs of it here.
SPOILER ALERT
What's worse in this book is that he sets up this awesome gigantic dog that is Sally's companion. He is clearly super dangerous and super loyal, but we never get him doing anything but sniffing and growling at potential enemies until one final scene, where it isn't even Sally being attacked, and he gets killed! Totally fucked. This is the animal equivalent of the Bechtel Scale and it is just lame. I was really pissed about the dog, but he does the same thing with Frederick, who was one of the great characters in the first book, a significant player in this one, the other half of their potential detective agency, an ally in fighting to young Jim and finally a potential love interest for Sally. He just kills him off and it felt cheap and manipulated. I don't really know what was the point in making this choice. It makes me lose confidence in Pullman as a storyteller. He feels that his own clever "breaking of the rules" is more important than the reader's pleasure. No bueno.