The "Where are your classics?" question is a late-breaker this year. I hadn't got that one until yesterday when I had three of them.
A sample conversation goes a bit like this:
Customer: Where are your classics?
Me: Well, we don't have a separate section. Some titles are on a display, but most are in their specific subject arranged by author. Is there a specific title or type of book you're looking for?
Customer: *blink blink blink* A classic.
"Classic" really isn't a genre. If you talk to a Classics major, then you get the Greek and Roman Classics which encompass philosophy, history, and drama. In more general terms, a classic work of literature is basically something approaching at least 100 years of age and is still read (more or less - this is one of those "definitions" that's become very elastic) and those span every conceivable genre and subject. Plain old fiction, romance, mystery, science fiction and fantasy, mythology, western, drama, poetry, essays, history, philosophy, cooking, sporting, economics, travel, religion, and on and on and on.
All classics are not alike. If you want something sort of crazypants and are a Lovecraft (who, depending on definition, is approaching classic author status) fan, then you're probably not going to be over the moon with Dickens. You'd be happier with Kafka or Stevenson. If you are easily offended, then don't read DH Lawrence. If you're looking for something short then Eliot or Milton are not good choices.
So when the bookseller asks if you are looking for a particular book or subject that might happen to be a classic piece of writing don't just say "classic." We do actually want to help you find something you like (or find something the recipient of your gift will like). Put some thought into your answers to our questions. "Anything" doesn't count as an answer.
Otherwise, we'll leave you alone in the corner to cry over the thickness of Don Quixote and War and Peace (and be assured, we have found the thickest copies we have).