Important things in my life come together: Miss Manners and librarians.
We had a librarian like that in my hometown. I remember going in once the year after college and going to the checkout with a stack of books. I had just decided to try reading Stephen King for the first time--seemed like it might be fun--so I had two Stephen King books, plus The Law of Love, by Laura Esquivel, who wrote Like Water for Chocolate. There may have been something else, but I remember these specifically.
And that's because I remember her commenting on each one. Not as rudely as the woman in the Miss Manners column; really just conversationally. Except she didn't like my choices, so it wasn't a great conversation. Of Stephen King: "Oh, I've never liked his books--" said with a definite snootiness. Of Laura Esquivel: "Oh, I tried reading her other book; it was over my head." Any snootiness there--of the, "If it was beyond me, you have no hope, honey" variety--just made me feel superior.
Now, a) I had read and enjoyed Like Water for Chocolate, and b) it seems like a librarian making conversation could come up with more than, "I hate all your choices." Hasn't she heard the rule about saying nice things or saying nothing at all? Is my mom the only one who taught that one?
I have to say, I don't feel Miss Manners gave very useful advice. Shushing the librarian may be all you can do, but I am not convinced that the kind of woman who needs that kind of shushing will respond to any hints that don't involve a blunt instrument.