u/Upstairs-Formal-6652

So I love reading, been doing it since I was a kid, but recently, maybe like 9 months ago, I focus too much on the book, and think about that too much (trying to understand it), that, ironically, I have to reread the same sentence again and again. I'm a fast reader and this ONLY happens with new books. When I read books I've read before, I finish them quickly because my brain isn't trying to focus and not miss out on anything, since in my head I'm like "Oh I read this already", and it's so much better. That's how I normally used to read old books and I remember everything in those. So how do I stop doing this?