I am an adult who struggles with reading. I can fully understand books up to about an eighth grade or high school level (books like Harry Potter, The Great Gatsby, writing of Hemingway, etc...) but I struggle with more complex works. I've recently tried reading Thomas Hobbes, Adam Smith, Bertrand Russel and other philosophical pieces; I've found that I have to put the book down after a few hours of straining my eyes because I have no clue what is going on in the reading, and I don't know why that's the case. Is it that the language is so much different from modern English? Is my vocabulary too much deficient to comprehend the variety of words used in these texts? Or am I just missing a lot of context surrounding the philosophical tradition? Or a mix of those...
Does anyone have advice of how to improve my reading skills so that I can digest more difficult works than The Hobbit?
(Side Note, I remember first noticing this problem in college when I read The Last of the Mohicans and answered every question incorrectly relating to characters emotions, arguments, and etc. My lack of reading skills, shockingly, didn't prevent me from completing a math degree and working as an actuary. This is wholly due invention of video and audio which I've turned to when textbooks were incomprehensible to me).