Just wanted to share an article I came across that talks about how Niffenegger got her start in writing her novels (versus her art and graphic novels), and also a good chunk on which books/authors have influenced her writing.
Here's the page:http://infloox.wordpress.com/2009/10/15/this-years-publishing-sensation-fairytales-do-happen/
I think it's so amazing that someone can write their very first novel and have it become so wildly popular over just a few years. Definitely an achievement to be proud of! (It's cute how she still sort of doesn't quite believe it) :)