Lunch time

In one of my favourite spots again. 

A pair of young children were wandering around behind me and I heard this delightful conversation:
Girl: What's she doing?
Boy: She's reading, so you have to leave her alone. [Well trained, I see]
Girl: What's she reading?
Boy: I don't know and it's none of your business.

I wonder how they would have reacted if I told them I was reading a book about JRR Tolkien's work on the Oxford English Dictionary...