There are two great powers, and they've been fighting since time began. Every advance in human life, every scrap of knowledge and wisdom and decency we have has been torn by one side from the teeth of the other. Every little increase in human freedom has been fought over ferociously between those who want us to know more and be wiser and stronger, and those who want us to obey and be humble and submit.
The Subtle Knife is a good fifty pages shorter than The Golden Compass, but I don't think that's why I read it faster (or why it felt like I did). There isn't much of Lyra here. The focus switches instead to Will Parry, a normal boy caught up in unusual circumstances. A lot of the mysteries presented in the first book are finally resolved (somewhat) in the second book, like the origins of Dust, and why Lord Asriel is hellbent in breaking the barrier into the other worlds. The pace is much faster, even if there are some tedious passages, and it fulfills its purpose of transitioning into The Amber Spyglass.
She felt a nausea of the soul, a hideous and sickening despair, a melancholy weariness so profound that she was going to die of it. Her last conscious thought was disgust at life; her senses had lied to her. The world was not made of energy and delight but of foulness, betrayal, and lassitude. Living was hateful and death was no better, and from end to end of the universe, this was the first and last and only truth.