Joe is very much a comforter and provider of others' needs and well-being, but also highly attuned to physical details, such as with the maintenance of the rare book collection. Despite where he lives in NY, he's also comfortable with being the not-so-shiny, ordinary bookeeper, someone who isn't given over to the hustle and bustle of the world around him. Someone who is capable of stopping and smelling the flowers, so to speak. Not given over to the pretentious aspirations that so many in his environment are given over to. He loves books and that's what he sticks with.
He's also not one for planning or forethought. He tends to improvise and live in the here and now, more like an S. Even when he assaulted a certain someone, he was like, "well now what? I didn't think that through." It's not the kind of long-ranged planning you'd see in types such as LIE or ILI.