Learning works if it makes you think; this is why most videos don't work. Watching TV you 'sit back' and turn off. How often does it make you think?
Books require some engagement - the activity is called reading. You think a bit of you takes notes. You think even more if you interpret what you read in a way that makes it your own. This is best achieved if there is a specific goal, typically to research and write a response to a problem addressed in an essay title. In the longer term to sit an exam or to write a longer piece, such as a thesis, or to give a presentation. To read without such application is to row your boat without a rudder.
If in the past I've said that is it 'time and effort' that leads to learning, then I'd now reduce two words to one. Thinking = time + effort.
What do you think?