Q: How did the idea of a magical treehouse come to you?
A: I'd tried many things to get kids back in time: a magic cellar, magic whistles, magic artist's studio, magic museum. Nothing was working and I was really about to give up after a year. I was walking through some woods in Pennsylvania near a cabin that Will [Osborne] and I used to have, and we saw an old treehouse that was all rickety and pretty well run-down. We started talking about, "What if I put the characters in a treehouse?" Because then it would always be hidden up in the trees and they could travel anywhere with stuff in it. Finally, that night, we thought it'd be cool to have the treehouse filled with books, because books are magic. The moral of the story is the simplest ideas are the hardest to find.
Q: After graduating college, you traveled with a group of other young people to various locations like Iraq and Pakistan and India – how did doing that traveling affect your writing of the series?
A: I was a vagabond, and what I realized was it was a lot safer to stay at home and be a vagabond. By writing the series, I got to indulge all my travel passions and still be home in time for dinner. [Through the books] I had been to or will travel to a lot of the places, but without a backpack anymore and without risking my life.
Q: What do you think it is about Jack and Annie that appeals so strongly to children?
A: Jack and Annie are ordinary kids, but they're really good kids. They're always trying to help others and they're very supportive of each other. They have a sense of humor, but they love reading and learning and they have great compassion for animals and people who need their help. The series is in over 100 countries, 33 languages, and [the kids] all identify with Jack and Annie. I find that so encouraging.
Q: You've said before that Jack and Annie's relationship is in some ways based on your own relationship with your siblings?