[Sequel to The Magicians.]
There are two storylines in The Magician King, the backstory of Julia’s training as a hedgewitch and Quentin’s quest for the seven golden keys.
Quentin, along with his high school crush, Julia, and his fellow Brakebills’ alumni, Eliot and Janet, have ruled Fillory for a few years. Bored with being King, he sets off on a quest, taking Julia with him. Unexpectedly thrust back to Earth, they desperately strive to return to Fillory, eventually succeeding. Magic is leaching out of the universe as the old gods awaken, and only the seven golden keys can unlock the back door that will save the magic.
As the main story proceeds, so Julia’s past unfolds. She auditioned for Brakebills when Quentin did, failed, and had her memories replaced. She realizes her loss and seeks magical training elsewhere, gradually leveling up through a series of rogue safehouses to an elite alternate institution, where original—and dangerous—research into the origin of magic is taking place. She attains great powers but at a huge cost.
Quentin, having been tempered in The Magicians, has matured and is readier (though not yet fully ready) to make the sacrifices that he will be called upon to make.
A satisfying middle book of a trilogy.