Be honest. It sounds a lot more interesting and compelling to hear someone explain an unexpected response, like a children's book or how to crochet a dog sweater, because you have room for a creative - and memorable - story. Don't feel like you need to respond with something likely found on the school's reading list if it isn't true or of interest to you. They want some insight into your interests and how you might be able to show your students that reading practice at home is valuable regardless of the content.