I have both things going on, you might say. When I first settle down with a book or long form reading after not having done it a while, it's a considerable effort to focus. Typically at some point after forcing myself back to the text and rereading paragraphs many times I will get immersed in the text. Focus improves and reading speeds up, and for a book I might binge-read it in a couple days, with it occupying my thoughts even when I put it down.