The characters were pretty boring. Some of them seemed to have interesting internal lives, and the sections of the book where the reader encountered a character alone were the best parts. But when interacting with each other they lost all dimension and the dialogue was flat and cliched.
The two little girls could have been given a lot more depth, considering they seemed to be the central characters of the book when they are first introduced. However, as the book goes on they have little interaction with the adult characters and seem more like stage props or pets. I guess, given the cover art, I thought the story would have been about the girls and that the reader would have been given more insight into their thoughts on being adopted, on growing up in American culture, etc. Just because they are children doesn't mean they can't have interesting perspectives on their situation.
Overall, it wasn't entirely poorly written, it was just boring and unengaging. Not to mention having to trudge through the pages and pages devoted to the "binky party," which really seemed to have no bearing on the rest of the plot at all.