Of course, reading a book is going to take some training. The nice part is that if one reads for 15 minutes to a half hour a day, it becomes fairly easy to focus on a book within a few days. As long as the book is engaging/interesting to its reader.
Turning the phone on silent and/or keeping it in another room while reading helps a lot as well.
I realized during a pre-Endgame re-watch that I liked a lot of the marvel movies better at home than I had in the theater, and after some reflection figured out that it’s because when I get really bored in the middle of one of their not-very-good 20-minute fight scenes, or awkward too-long exposition, I can just screw around on my phone.
On further reflection it occurred to me that this kinda replicates the experience of watching a mediocre movie with a close friend group and just talking over a bunch of it. Lots of movies are better when half-ignored!
Of course, there are plenty of movies where you’ll have trouble following them or miss cool, interesting, very-good, or important elements if you don’t give them your full attention. But I do think there may be a case for phone-in-hand film-watching. Some might argue that you should just skip any movie that gets better if you partially-ignore it, but I’m not on that boat.
That's more likely from dopamine being fried from screens and instant gratification than a statement about the quality of books.
I got back into reading about a year ago, and it took me a month before I could read like I used to as a kid, fully immersed, let the world disappear kind of thing. I was looking up every minute before that with a strong urge to grab my phone.