I read this when it first came out in the US, I was 8 or 9. I reread it many times, partly because I enjoyed it and partly because it seemed oddly familiar. When I escaped the white supremacist cult in which I was raised, I left my copy behind and forgot about it for many years.
I recently bought another copy and reread it for the first time in over 20 years. Now I understand my strange childhood fascination with the book and why I had to hide my childhood copy from my mother, who disapproved of it. Had I been living in a rural area rather than in Chicago, I probably would have realized at the time that it was my own story.
This book is appropriate for kids that age, although I think an adult who can answer questions about it would help. As an adult it took me a couple hours to read, and the suspense was gripping. At times the dialogue seems odd and pointless, and there's some telling rather than showing.