I try to be methodical when reading - by taking notes or highlighting things and then going over those items later. I also try to make sure I understand everything before moving to the next chapter - this doesn’t mean I have to remember it all, just understand what’s going on before moving on. I will happily read a chapter more than once if it feels like something hasn’t made sense.
I will also only read books that appear to be on my wavelength - there’s no point trying to read a book if you just don’t click with it. This is also one of the reasons I prefer professionally published books, they’re usually of a decent quality and an editor has usually made sure the information is accessible and easy to understand. Reading a book is a big investment of time, hence I prefer the highest quality if at all possible.
I have more tips here: My best tips on learning/reading/studying!
Something I have found though (and I wonder if any of you have too) is that I find it harder to get into the mindset to read, and I think this is because of how our brains are changing thanks to social media/dopamine hits. I read recently that young people can only concentrate for short bursts now, I find that worrying.
There is a way around it but it takes some discipline. From my post above:
With this technique and enough discipline (i.e continuously over a few days) you can get back into studying/reading… just like we did in the old days 
(If anyone tries it, let me know what you think!)
