My favorite of her books is most definitely Traveling Mercies. If you haven't read any of her material, I highly recommend starting with this one. I'm much more of a memoir reader than a fiction reader. Anne Lamott has written both, but in my humble opinion, her fiction does not rise to the same level as her memoir writing.
I am excited to discover that she has a new novel coming out this spring entitled Imperfect Birds. I will certainly be checking it out.