There are precious few satisfying answers to the question above. I have gone to the trouble to list them for you here.
“Oh, I dabble in literary fiction, you may have heard my address at the Nobel Prize acceptance ceremony?”
“Joanne Rowling. Lovely to meet you.”
“Mainly plays. Probably nothing you know. Ah, you’ve read King Lear, have you?”
Or even: “Very few, actually. I’ve barely put pen to paper since dashing off Catcher in the Rye back in the 50s.”
What you don’t want to say is this:
“Well, I’m technically speaking a children’s writer, but not entirely, I mean, older children, some not children at all, many perfectly sentient adults, in fact, seem to like my books, which do, of course, feature adolescents, but often incorporate quite difficult themes, say, on the subject of life and death, and funnily enough I’m published for adults in the US, though possibly not for long, and many of my Finnish readers are over 50…”
You really don’t.