One of the features of the new world is that everyone has a "feed," which is basically their own blog/myspace/tv channel. The ratings of your feed (combined with how much the city interface overhears people talking about you) determines your social status--so everyone knows at all times how famous they are. As Scott Westerfeld explored the themes of extreme beauty in the first three Uglies books, now he takes on the world's obsession with fame and popularity. And how anyone can be an instant celebrity.
I think that at the end, Aya should of realized it isn't all about fame and became more like the Sly Girls, not caring about popularity and having fun on dangerous hover board riding. Aya should of NOT be so obsessed with her face rank, and gotten on with her life, one without the fame, she should of learnt what happens with it from her brother.
The languages as well were very confusing, and the location of the story to. I had no clue what so ever that Aya and her friends spoke Japanese until halfway through the book, and this to panic from me in the form of flicking back through the pages. And the location of the city was never said, not even the name of city in fact.
Over all, if you enjoyed the last three books of the Ugly series, than Extras is worth the read, but be warned, it is not as awesome as the others, but still pretty good.
-Tally and the Cutters coming back