I loved this so much the mythology was so interesting and the different characters were fascinating. The mental illness rep (PTSD and depression) was a bit brutal but very good from my perspective (I have both but from different causes than the characters). I would recommend caregivers find and read those sections first and maybe have a talk with a 10 and up child about them before having them read it, but other than that I think this is very accessible and would be very interesting to MG aged kids. There are also themes of divorce (parents of the protagonist), grief and death that are accessible and might be a good way to initiate or continue discussions of those things with kids. All of it is handled in a very hopeful way.