I block out time, set a timer and put everything away.
Then I read till the timer goes. Sometimes it's easy. Sometimes I just stop and zone out. But I don't stop to check my phone or whatever else could distract me.
I assume you mean non-fiction. If so, the rules outlined in “How to read a book” are a good place to start. It’s been a while since I’ve read it.
Write down your motivation for reading the book. Do whatever you want until you feel like taking a break. After the break, write down reflections on what happened. Repeat.
This works for anything, not just reading books.
Read on the subway, where there isn’t a reliable internet connection.