I’ll admit I saw the film version of The Golden Compass first, but I just finished reading the book by Philip Pullman, and the same elements are all there, if slightly rearranged and quite a bit harsher than the movie.
Lyra is a precocious 11-year old orphan living in a world mostly like ours, but with a few major differences – one being that all humans have an animal-shaped “daemon” which accompanies them throughout life, a manifestation of their own soul. So Lyra’s daemon Pantalaimon is her first and constant companion. One day Lyra is hiding and eavesdropping on the scholars at the college where she lives, when she gets pulled into matters far beyond what she can comprehend by her Uncle Asriel. Then her friend goes missing (along with many other children), apparently kidnapped by unknown forces they call “Gobblers,” and Lyra vows to rescue him. She is given a precious gift called an alethiometer (the “golden compass”) and told to keep it secret and safe. Next, she falls under the spell of the charming Mrs. Coulter and travels with her for awhile until she discovers her real intentions, at which point Lyra flees.
SPOILERS In her quest to bring the alethiometer to her uncle in the far north (which she believes to be of utmost importance), and to rescue her friend Roger, Lyra faces many hazards and acquires a large number of companions, including a gyptian king and advisor, an armored bear, a witch, and an aeronaut (all but one of these is male, as per usual for GU companions). She must thwart Mrs. Coulter, and eventually Asriel as well, even after they are revealed to be her true parents (though they are even more distant than the usual GU parents, barely seeming to care for her at all and happy to let her believe she was an orphan). [While I have seen many examples of the adversary being a stepmother, this story cuts deeper by having it be her own mother.]
In the end, after leaving all her companions behind and venturing forth alone into the unknown, Lyra ultimately loses the friend she had rescued, and finds that Asriel wanted something far more sinister than the alethiometer after all (exposing him as a second adversary). Her dangerous journey might have been for nought (although she did rescue many other children), but instead she takes the opportunity to embark on an even more perilous adventure (continued in the following books of the trilogy, which I have not read yet).