Obviously, a character will use their skills as-is to see if they know something on the field. But are there any rules for getting a bonus on a check if you have a library or some similar reservoir of knowledge (maybe even just a book on the appropriate subject, rather than a whole library) as a resource? Or is it just assumed that you can find whatever info you need if the library has an appropriate book somewhere among the shelves?
There are some basic rules on page 98 of Covenants. You essentially get a bonus of +1 - +5 on your Int + Ability roll depending on how good the library is in the subject.
Covenants, page 98.
There are also some rules in Art & Academe regarding using encyclopaedias for research. No access to the books just now for page numbers, but you'll find them in the Philosophiae chapter, under Natural History.
Page 26. It's the boxout just BEFORE natural philosophiae.