Pharaoh's of Ancient Egypt for module 1

I am about to start using module 1 with my kids.  I see the book “Pharaoh’s of Ancient Egypt” is scheduled for my 4-6 grader to read by themselves.  I was looking at the tapestry of grace website and they have this book scheduled for their rhetoric students (grades 10-12).  I am wondering if this book is going to be too hard for my 4th grader to read and comprehend.  Has anyone else used this book with a child of this age, and how did it go?  I am wondering why TOG has it listed for high school and SCM for elementary age?  Any ideas why?