I've been meaning to re-read this series for a while now, partly because I read Paradise Lost recently and feel like that might add a whole new dimension to it...and partly because I don't think I really appreciated it the first time around...and partly because DAEMONS.
So Northern Lights follows Lyra, a twelve-year-old girl growing up in an Oxford not unlike our own, apart from the fact that every human has a daemon, a sort of externalised soul who takes the form of an animal. When children begin to disappear from the streets of the city, stolen away by a shadowy agency known only as the Gobblers, Lyra departs on a journey to the far North to try to discover why and where they have gone.
One of the things (out of a multitude of things) that I like about Northern Lights is that it's realistic about what a twelve-year-old can actually achieve on her own while still allowing her to shine. Lyra's friends - grown-up friends, friends with actual agency in a realistic world, no Mr Tumnuses here - help her and protect her on her journey, and their concern for her feels genuine and touching (Iorek Byrnison, I'm looking at you), yet at crucial points she gets to steal the scene, as it were. She prevents massacres, rescues daemons, tricks armoured bears in ways which are undoubtedly impressive but which never feel forced or contrived in any way. Lyra is, simply put, a kick-ass heroine.
I was also mildly surprised at how complex and profound Northern Lights is, and I think this is why it makes such a successful crossover book. There's a lot of stuff about the power of the Church, about ambition, about cruelty, about quantum physics (yes, quantum physics) that I know for a fact went straight over my head when I first read it. It's a book that works on two levels: it's a fantastically inventive story, constantly refusing to give a simple, easy ending, full of tragedy, yet refusing to give up hope; it's also a questioning of the world, of the nature of knowledge, of self-sufficiency and contentedness, of friendship and childhood and meaning. It's possibly the least patronising piece of YA I've ever read.
(Mind you, this is a childhood favourite, so I'm probably biased.)