Please declare aloud: I hereby undertake to tread the world, to garden the wild, and to saddle the seals, as did my brother Brendan. I will not turn away from shades in fear, nor avert my eyes from light. I shall do as my Keeper requires, and keep no secret from a Sage. May the stars guide me and my strength preserve me. And I will not smoke in the library. Translation approved, 1946.
Book 1 of the Ashtown Burials series by N.D. Wilson. Perhaps you've read 100 Cupboards?
Also, I cannot emphasize this enough; no smoking in the library.