What Motivated You to Write Your Second Book?

I love your books. I'm recommending them to people like all the time. But books are not iterative. For people who like to experiment and test and change, a book is probably the most water-fallish type process you ever go through. Will I ever write another one again? Who knows? People say, I've not given birth, but maybe it's like running marathons for me. And it's a challenge, but it's very rewarding. What I learn along the way inspires me to keep looking for new things.