The Golden Compass is told by a third-person omniscient narrator. This means that the narrator isn't a character in the story, just a voice that knows everything that's going on in the world. That said, the narrator sticks close to Lyra and only tells us what's going on around her. The narrator rarely leaves her and tells us about what Roger is doing in Bolvangar, for example, when he's separated from Lyra, or what Lord Asriel is up to until Lyra finds him in the North.
How would this story be different if Lyra was narrating her own story? Do you think you'd like it more or less? Why do you think Philip Pullman decided not make Lyra the narrator?