** spoiler alert ** 
 It actually took me a while to get through this, and it's of no fault of the book as it was awesome with some very nice additions to the first book. The whole vibe of it shifted slightly and became much darker and I really, really loved the addition of Will into the cast. The torturing of the witches, and the addition of spectres kinda raised it above the last one just in terms of the subject matter. As a book that's considered a children's book, it's actually quite brutal in places. 
 The way the book ended with Lyra kidnapped, Will having to find Lord Asriel, the addition of angels and the spectres lurking is something that makes reading the third book a neccessity.