(Delay in posting due to snow days, etc., may or may not persist.)
The Magicians, the book, the first one in the series, presents itself as a story about the friendship between Quentin and Julia, though in an attenuated way. Julia appears at the beginning of the story, as one of Quentin’s two cooler friends, along with James, who she may or may not be dating (I can’t remember whether this is stated in the book). She disappears almost immediately. Quentin goes to his Princeton interview (not Yale) with James, who’s also interviewing there, and immediately afterward is transported to Brakebills, cutting short his senior year in high school to start college early. Julia doesn’t reappear until his next vacation at home, when she confronts him and reveals that she resents the fact they didn’t choose her, too. (James never reappears at all.) Around that time, Quentin’s family moves from New York City to a suburban New England town much like Lexington.
That’s it. All of the rest comes up only in the second book, where it’s told in flashback, as an explanation of how Julia had become the difficult, unhappy woman Quentin later meets in Fillory, and of how she managed to get there in the first place. The TV series sets the two stories more in parallel, so they’re both at similar points in their education at the same time. But with this episode, the friendship between Quentin and Julia seems to be replaced by two new friendships that don’t really have a place in the books: between Quentin and Penny, at Brakebills, and between Julia and Marina, in Brooklyn. (There’s no character corresponding to Marina in the books in even the slightest of particulars, except that Julia does meet a bunch of independent magic-adepts, and some of them are women.) And that’s fine.
In the third and fourth episodes, Julia and Quentin interact, in ways that show Julia and her friends messing with the Brakebills crowd. First, they steal a book from Quentin’s house, something for which he and his housemates are going to be held responsible (Brakebills is apparently the only institution in the world that’s permitted to have books of magic, and from the novel we know they have a hair trigger when it comes to expulsion), and which leads to a physical confrontation. Next, Julia takes revenge on Quentin by (under Marina’s guidance) putting him under a spell that causes him to black out after a party and dream that he’s been committed to an institution after trying to kill his father. So, in the series, instead, it’s suggested that Quentin is going along happily in his grad-school career, when Julia somehow derails him at a distance.
As a result of this, we see that Quentin is learning to trust and respect Penny. Penny knows how to help Quentin because he can read Quentin’s mind and tell him how to get out of his own web. Quentin’s shaping up as a sort of mediocre kind of magician, so far, and Penny (though, to the dismay of his roommate, he’s not white, not upper class, and not nerdy looking in the right way) is a better one.
While this is going on, Marina is serving a similar role for Julia. But while Julia has understood Marina, so far, as an outsider like her, someone who’s gotten where she is by grit and hard work, Marina all along has thought of herself as a rightful graduate of Brakebills, whom fate has separated from what’s rightfully hers. She kicks Julia out of the gang for betraying her, after she uses Julia’s connection with Quentin to get access to the Brakebills grounds herself, and after reacquiring the knowledge Brakebills was withholding from her, removes Julia’s ability to use anything she’s learned.
Needless to say, none of this is in the book. In the novel, there’s a sense that Quentin feels at fault for Julia’s unhappiness to the extent that he was her friend and he failed to think about her, and that he tries to make it up to her. It isn’t suggested that his going to Brakebills has anything to do with her, or that the path she chose has anything to do with him. By moving up Julia’s storyline, the series creates a feeling that the same thing might be happening to the two of them in different ways.