It's a bit strange that we all are surprised our attention spans have seemingly shrunk. Almost everyone has multiple screens and notifications yelling at them all day long now. We are training our attention spans to be shorter and react to notifications.

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.