The Amber Spyglass is no doubt the emotional and philosophical heavy weight in this series and probably the most important book in the trilogy as it is where all of the ideas and overarching themes come together. But The Subtle Knife is my personal favorite of the series. It’s the book that introduces Will Parry and it’s the one that completely hooked me. It also introduces Will and Lyra to one another and I love how their friendship slowly grows and the tension between them and the little hints that there could be something more. Plus the plot of this one is really fast-paced and I think the easiest to get through out of the three books.