Relax. This book's language and themes are pretty straightforward. This is about the hardest it gets:
I wondered if my mama, wherever she was, had a tree full of bottles; and I wondered if I was a ghost to her, the same way she sometimes seemed like a ghost to me. (14.44)
She's trying to figure out if her mom misses her, so the language gets a little figurative. But we think you can handle it.
Still, this book isn't just for nine-year-olds, even if it claims it's for kids nine and up. It was even a New York Times bestseller, for crying out loud. Why? Because it's about life. It uses a ten-year-old's thoughts and ideas to make everyone, from nine-year-olds to ninety-year-olds, think about what's really important. So anyone can read and learn from this book. Scout's honor.