My mom, an english teacher, once went through my library of science fiction and analyzed it for reading level. I had the usual collection: Lots of Heinlein, Asi

My mom, an english teacher, once went through my library of science fiction and analyzed it for reading level. I had the usual collection: Lots of Heinlein, Asimov, Niven, Andre Norton, etc. Her assessment: Most of the material was about 8th grade level, based on word count. From time to time I re-read one of those books, and run across pages where she had penciled-in notations and underlined words.