She reminds me a lot of Diana Wynne Jones -- twisty plots, very human characters with hidden depths to them -- though her books are less happy-go-lucky than Jones' often are, with a sharp bite to them. Fly By Night totally sucked me in with its world-building -- floating coffee shops pulled by kites, banned books and hidden printing presses, a complex web of deceptions and lies hidden in more deceptions and lies. Well Witched is more of a people book, as much about the interactions and personalities and flaws of its three young protagonists as the supernatural situation they've been thrown into. Fly By Night falls more on the adult end of YA (it reminded me of Phillip Pullman's books in some ways) and Well Witched is more in the Harry Potter, "kids having adventures" mold. In both books, though, she's got a sharp eye for humanity -- how they fail, how they succeed, why they do the things they do. One of the things I love most about her books (as with Jones') is how often characters are not at all what they seem at first -- everyone can be brave, and everyone can be a coward, and it's circumstance that creates heroes and villains, more than any sort of innate hero-ness or villainy.
Highly recommended! (And if anyone on my f'list has read either book, I'd love to discuss them!)