As someone else with ADHD(-PI), I think part of the answer has to be removing the potentially distracting stimuli. Online content draws your attention much more

As someone else with ADHD(-PI), I think part of the answer has to be removing the potentially distracting stimuli. Online content draws your attention much more easily than books will. I’ve found that I often won’t get back to reading a book until I make a concerted effort to get away from my phone, computer, etc. Only when I’ve eliminated the more distracting options will I get back to reading. It’s hard to get started, but it’s invariably more satisfying after the fact.