The world has been printing books for 450 years and yet gunpowder still has a wider circulation. We don't go around murdering people in libraries these days. In detective stories, virtue is always triumphant. They're the purest literature we have. Libraries are accepted as such respectable institutions that when they are involved in murder, the melodramatic element is more prominent.
Librarians are wonderful people.
They should be in the detective business. We are librarians, and therefore the elect of God. To read is human, to catalogue divine. For fear that the gallows be thine end.