One thing is for sure: she's Ethan's connection to his mother. This is a double-edged sword. Not only does she remind Ethan of things his mother used to do and love, she also, well, reminds Ethan of things his mother used to do and love. It's bittersweet—both a reminder of love and a reminder of loss.
It's appropriate that a librarian is the keeper of this knowledge, but this particular librarian also knows much, much more.
Marian has two jobs—both of which she inherited from Ethan's mom. Her day job is as librarian of the Gatlin County Library. Her night job is as the Keeper of the Caster Library. Think Giles from Buffy the Vampire Slayer.
The Caster Library, also known as the Lunae Libri, is a little bit different: it's underground, it's full of enchanted books, and has catacombs and tunnels so long and winding that even Marian hasn't seen them all.
As the Keeper, Marian says she's a neutral force—she can't interfere in Mortal nor Caster politics. But boy does she find some loopholes. She has Ethan and Lena's best interests at heart and she quickly takes Lena under her wing and makes her feel like a member of the family.
Marian may be warm and loving toward Ethan and Lena, but to some of the more difficult residents of Gatlin, she is anything but. And to prove herself, she has the most powerful weapon of all: her brain.
Marian's specialty is quoting literature—she might just have every book in the Gatlin County Library memorized. From Shakespeare to Oedipus, Homer to Martin Luther King, Jr., Marian has a quote for everything and boy does she know how to use them. She and Macon make quite the team when they verbally attack the disciplinary panel at the hearing to expel Lena. A woman who knows how to quote literature and use those quotes as well-placed comebacks is a woman after our own heart.
One last thing: Marian and Ethan's mom, Lila, worked on numerous books together. Hmm, two female partners writing a book. Sound familiar? If not, check the cover of your book. In fact, the last book Marian and Lila were working on was a romance, one about star-crossed lovers who were doomed to not be together. Coincidence? We think not.