Moving down a level

I just started using Middle Ages, Renaissance, Reformation, & Epistles with my 14 yo son (9th grade). We have gotten to the lesson which requires that he read The Story of King Arthur and His Knights. He struggled to read the Prologue, so I read it back to him asking him to narrate as I read each paragraph. Today, I read Chapter 1 to him, again asking him to narrate each paragraph due to his lack of understanding of the old english style of writing. His is simply struggling so much with this that even when I read it to him he isn’t getting it. Should I move down a level and have him read the book for grades 4-6 The Vikings? Or, just push through it one paragraph at a time?