The “extremely overdue library book” has had a long run as a sitcom trope. As a source of humor, the ludicrously large library late fine pays off in at least two ways: first, there’s the enormity of the fine when compared with the insignificant monetary value of the book itself (paving the way for jokes about inflation and compound interest); and second, there’s the idea of the “criminality” of the offender, who is probably unlikely to commit any other kind of crime, with the concomitant image of “library police” (or actual police) coming after the negligent borrower . . . One day, that could be you, dear reader.