It's the diary of a twelve year old girl who's living in a New York City (and an America) that's slowly falling apart. As the story progresses, her family slowly (and then rapidly) falls from the upper-middle to the working class, But what's even more fun is that her language completely changes! For instance, here's the first paragraph of the book:
Mama says mine is a night mind. The first time she said that I asked her what she meant and she said `Darling you think best in the dark like me.' I think she's right. Here I am staying up late tonight so I can write in my new diary. Mama gave it to me for my birthday today. I love to write. Mama and Daddy write but I don't think they love to write anymore, they just write because they have to.
And here's a randomly selected paragraph from near the end of the book:
While I waited I hid the bat alongside the stoop between trash cans then stairsat watching cars swoop past. His street wasn't much for walkers and that pleased cause I didn't keen interference. The light outside his building burned out and that heartened cause the darker the better when it all downcomes. Sitting there I photoed his puss in my head the way he cursed Daddy and Mama and lied on Daddy's paycheck and his billing five dollars and I steamed set to boil. There was no excusing what he did none nada none. Every time I heard the clipclop I eyed round but it never was him even after nine. I didn't leave though.
The language changes so gradually, though, that you hardly notice. A few new words get introduced her and there, and then a few more, and there's never a moment at which you're like, "Wow, this is now a completely different voice!" It's a pretty remarkable performance.