His Dark Materials by Philip Pullman
Northern Lights (a.k.a. The Golden Compass)
Lyra Belacqua is content to run wild among the scholars of Jodan College, with her daemon familiar always by her side. But the arrival of her fearsome uncle, Lord Asriel, draws her to the heart of a terrible struggle—a struggle born of Gobblers and stolen children, witch clans and armored bears. And as she hurtles toward danger in the cold far North, Lyra never suspects the shocking truth: she alone is destined to win, or to lose, this more-than-mortal battle.
The Subtle Knife
Lyra finds herself in a shimmering, haunted underworld—Cittàgazze, where soul-eating Specters stalk the streets and wingbeats of distant angels sound against the sky. But she is not without allies: 12-year-old Will Parry, fleeing for his life after taking another’s, has also stumbled into this strange new realm.
On a perilous journey from world to world, Lyra and Will discover an object of devastating power. And with every step, they move closer to an even greater threat—and the shattering truth of their own destiny.
The Amber Spyglass
In the astonishing finale to the His Dark Materials trilogy, Lyra and Will are in unspeakable danger. With help from Iorek Byrnison the armored bear and two tiny Gallivespian spies, they must journey to a dank and gray-lit world where no living soul has ever gone. All the while, Dr. Mary Malone builds a magnificent Amber Spyglass. An assassin hunts her down, and Lord Asriel, with a troop of shining angels, fights his mighty rebellion, in a battle of strange allies—and shocking sacrifice.
As war rages and Dust drains from the sky, the fate of the living—and the dead—finally comes to depend on two children and the simple truth of one simple story.
My thanks to Jeff for the heads-up about the gay content in books 2 and 3. Add your review of any or all of the "His Dark Materials" books in comments!