The Golden Compass

Twelve year old Lyra lives in a fantasy version of our world with a mix of magic and steampunk vibes. Children are mysteriously disappearing, and Lyra and her shapeshifting daemon, Pantalaimon, set off on a journey to uncover what has happened to her best friend, Roger. Along the way, Lyra faces off against corrupt adults, meets talking armored bears, and uncovers a secret plot. The book plays a lot with the concept of growing up, and it is the first in a series.