I don't have any recommendations for books on focus/self help etc but some general advice would be to think of a topic that interests you in other aspects of life and find books about that. Also physically move yourself and electronic devices away from each other if that is having negative effects.
In my case I started reading books that were adapted from movies/TV and video games. Stuff like Metro 2033, The Expanse, The Martian, Silo, Jack Reacher, The Bone Collector were what started me off. Then that leads on to other book series from the authors and so on.
As for my phone I leave it in another room when I feel like I need to focus. Not having it in arms reach and out of sight is a huge help.
This is good news. Arguably should have happened a long time ago but still, good that it is finally happening.