New York is a writer's city. Everywhere we go, there's inspiration. When my son was young and played in Union Square, I was moved to write The Elf of Union Square. Did elves always have to live in quaint, old-fashioned settings? Couldn't there be an urban elf lurking around our playground and Greenmarket? City kids have their own distinct experiences and cultural references, and the excellent kids' books below double as love letters to our rich, busy, complicated city.