This is a great book that is fantastic for kids 11 and up. I don't think 10 and under would understand this book so that is why I say 11. Your kid may be ready for it before 11 but I'm not saying they will completely understand it.
Willow is a lovable misunderstood 12 year old girl. She is a genius in everything medical and plant related. The only thing about this book is it can be a little bit depressing. Not quite TFIOS depressing but it will make you think about what you would do if both your parents died and it made me sad.
I know I'm rambling but all in all a 1/5 violence, 0/5 sex, 0 or 1/5 swearing, 2/5 consumerism, and 1/5 drinking/drugs/smoking