As a storyteller, I have to say this show does awesome things with characters. No one is a flat character. They all have masks and secrets. Everyone has their own goals, their own reasons to lie, and no one's exempt. Even the heinous mother-in-law character which most shows would leave as obnoxious and "there for the best interest of her daughter" has another layer in this show. Her self-sacrificing isn't really self-sacrificing. Of course she can move across the country to be with her daughter's family because she got fired from her job -- and hasn't told anyone. And that's just the mother-in-law character. All the characters are treated with the same sort of care. That sort of depth in storytelling is what makes stories fascinating.
And it's the kind of thing that keeps me up half the night reading, or in this case, watching.