If you're concerned about losing focus per "session", I would take it in small doses. Start with the big picture ideas first, then narrow the scope each time you study to add more and more understanding and nuance.

If you're concerned about losing focus long term akin to losing interest in the topic, I'm not sure I can help much other than read the news and watch interviews and discussions and debates around the topic and focus the inevitable anger that arises from everyone misunderstanding the topic into learning it so you can push back against the "socialism is when government does things" drivel

Sometimes I prefer to listen to an Audio book while doing something else like going for a walk or playing solitaire. Especially for more dense theory I will listen to the book a few times while doing other things and then I will read along with it one time to really lock the ideas in.