The third book tracks both Quentin on Earth and Eliot and Janet on Fillory. All three have matured greatly over the series, a satisfying development and one that suits Grossman's reworking of fantasy tropes. Several loose ends are also wrapped up, although there is a bit of an unfinished quality to the narrative. But then, that's only fitting since much of the story is about what happens after you graduate from the magical school/come back from the magical land.
As much as I enjoyed the trilogy, however, it took me until the climax of the third book to realize what it was the bothered me about it, and it is the lack of a moral center. Grossman is a smart, inventive writer, and is quite insightful when it comes to the trilogy's themes of maturity, responsibility, and the need to find a meaning in life. But the characters (and narrative) are concerned, ultimately, only with themselves and the people around them. It's a world where there are magicians, formally educated or "street smart," disciplined or wild, but there is little mention of a code of conduct or guidelines for interacting with the mundane world. The characters care about each other, and make efforts to do right by each other and their charges, but there is no concern with "the greater good." Niffins are wild, evil creatures that were once human, but while the return of one niffin's humanity is touchingly handled, the moral dimension is almost completely ignored. The climax of the third book deals with the time-honored themes of a deity's sacrifice and the cycle of death and rebirth, but where genuine self-sacrifice, and sacrificial love, suffuse the Narnia books and even the last Harry Potter novel, the sacrifice portrayed here is anything but; because it is imposed on the unwilling victim, the brutality and cruelty of it cannot be elevated into something meaningful. It is a very pagan scene, and it fits with the worldview Quentin has:
The world was fucking awful. It was a wretched, desolate place, a desert of meaningless, a heartless wasteland where horrific things happen all the time for no reason and nothing good lasted for long. ... The world was a desert, but he was a magician, and to be a magician was to be a secret spring -- a moving oasis. He wasn't desolate, and he wasn't empty. He was full of emotion, full of feelings, bursting with them, and when it came down to it that's what being a magician was. They weren't ordinary feelings -- they weren't the tame, domesticated kind. Magic was wild feelings, the kind that escaped out of you and into the world and changed things. There was a lot of skill to it, and a lot of learning, and a lot of work, but that was where the power began: the power to enchant the world.But it is not a worldview I share.