Contains spoilers
I really loved this book. I think it is the only book that really kept me reading without ever boring me. It is more dark and hopeless than the first book, and it introduced a lot of new concepts and plot points. It is full of action, there is always something happening and you can feel the constant tension that pervades the story, it even manages to be more deep about some topics without feeling pretentious or blatant. The characters are always under a lot of stress and difficulties, and it allows to see more of their nature and personalities.
The new characters were all likeable, Will, especially, was a really interesting character. In regard of the already known cast, it was a pleasure to read more about them since they were not so explored in the first book. But I missed the most important one: Lyra. In this book she feels different, in the first 2/3 chapters she seems almost out of character. It's not all for the worse, we can see her becoming more mature, having doubts, failing, and I think it adds depth to the character. At the same time, she felt almost useless in some scenes, like the fighting scene on the tower, or when the kids are trying to kill them in the temple, she doesn't do a lot, Will always overshadow her and that felt like a betrayal to the character if you compare her to the first book.
One of the thing that I appreciated the most is still the idea of daimons, often the author gives some detail about these relationships and how they works, like when Lee and Hester die, or with the relationship between Will and Pantalaimon and many other scenes. I really liked that this book adds more fantasy to the story, even if sometimes these fantasy elements are not so well explained and I hope that with the third book this problem will be solved. Especially because there are too many things that feel almost lazy: Marisa and Asriel are too much powerful without a reason, Marisa can see witches through their enchantments, and control the spectre/ghosts/spirits, Asriel builds an enormous castle out of nowhere, and they kinda control what happens with their wills. The witches are always saving Lyra at the last minute like they know where she is (and it seems there is a reason), the alethiometer acts strange, ecc...
To conclude, I think this is a great set up book for the third one, so most of my enjoyment comes from the faith that I put in the third one, because most of this book flaws come from the fact that it doesn't spend much time on explaining the mysteries surrounding the story.