After reading those, some of Giffen's other books, and now the Heart of the Matter, I've decided that Giffen excels at character development.
Plot: Tessa is a wife and newly minted stay at home mother of two with a busy life in her suburban community. Her husband Nick seems to be perfect -- handsome, kind, and a pediatric surgeon. But when he meets Valerie, the single mother of one of his patients, things change. The central plot in enhanced with great supporting characters, like the suburban queen bees written in true "desperate housewives" style, and a sweet little boy who's caught in the middle.
Each chapter alternates between Tessa and Valerie's perspectives, illustrating both sides of a very complex story.
Characters: As I said, this is where Giffen shines. I love that she alternates perspectives, and that she can make it happen with such ease. As a reader, it keeps me interested -- just when I'd hit a critical point with one character, the perspective would change. But it'd only serve to keep me reading. In addition to making the book a page turner, the differing perspectives makes it hard to choose a side. It makes you see the whole story.
Overall: In my opinion, it's rare for a book to keep me neutral. To not hand me the protagonist and antagonist in a neatly wrapped package. To make me assess the facts and make my own decision as to who's the "good guy". Giffen's books do this and for that, I'll keep reading. 5 stars.