Difficulty focussing while reading books (Not Learning Difficulty)?

That happens to me too, I am currently reading Pride and Prejudice and some of the words I can't understand so our brains skips them. I am reading and I find myself on another chapter when I cant remember anything before. Almost like a mini blackout isnt it lol? It could be bordem or it could just be giving up when you dont understand. I can't give you a great answer but only an answer to reasure you it happens to me too lol :)