Let me say something before I start the review:
The book is amazing.
The first paragraph makes you want to read the book, not even, the COVER makes you want to read it! The word choice paints a picture in your mind, and you feel as if you know the characters and care for them by the time you are finished.
While there are some curse words, I think tweens that can handle that should be able to read the book. Definitely no one nine or younger, I must say, and ten might be iffy, but eleven is ok and twelve and up is definitely a yes.
Hope this helped! Happy reading!