I'm not entirely sure of what I thought of this novel.

I find the second book of a trilogy often suffers from a 'mid-book problem' in which much time is taken up getting from the end of the first book to the final action in the final book. Pullman gets around this by introducing a new major character and taking the story in (what feels like) a substantially different direction.

Things do start to come together towards the end of the book, but I don't think I will really know how I felt about The Subtle Knife until I've read The Amber Spyglass.