Still a secondary character, but the librarian in Nick O'Donohoe's Crossroads trilogy (out of print, sadly -- it is SO GOOD) is very good at librarianing. The protagonist (a final year vet student whose professor has unexpectedly invited her to go on a secret rotation where they treat mythical beings) shows up at the library of the University of Western Virginia and asks the librarian (a normal, non-supernatural librarian) for practical medical information on unicorns. So she helps the protagonist with the catalogue, and they find some information.

Later on for plot related reasons she really does have to take out the library's only copy of a very rare book and give it to someone who she knows will not be giving it back (implication: because it will be destroyed[*]) and while she does it, she also has the sort of crisis of conscience about it that normally in TV and books you get to see doctors or lawyers having about betraying the ideals of their profession, not librarians. That was very good.

(Also there was a nice averted trope thing where the protagonist (who in fairness has been faced with a lot of actually supernatural or non-human people in plain sight, asks the librarian if she's a dwarf, i.e. the fantasy race, and the librarian, who is a human with dwarfism, very politely makes it awkward for the protagonist.)

[*] Not because the information in it is too dangerous, but because it's the only weapon that can defeat the baddie.