My protagonist Irene spies for the Invisible Library: a secretive inter-dimensional organisation. Its purpose is to acquire books (by any means...) from thousands of alternate worlds. And this helps supply balance to the multiverse. This also lets the Librarians pursue their private literary obsessions - but that's just icing on the cake.
The Library doesn't actually observe Christmas as a holiday. (In fact, they don't observe any specific holidays, and personal leave is handed out strictly at the discretion of a Librarian's own supervisor.) To the surprise of junior Librarians, giving and receiving Christmas presents between Librarians is tends to be discouraged. This often causes confusion. Surely giving presents is a sign of cooperation, of friendship, of sisterhood or brotherhood or whatever family relationship you like to idolise? How could this possibly go wrong?