Repetition and flashcards will help you remember the content, but it won't help you understand it. That's only done by actively engaging with the content and connecting it to and comparing it with other facts and ideas.
The summarising, keeping lists of questions, and writeups will help you understand the content, and I think is the only valuable part of this process. Why rote memorise when you have lovely writeups you can refer back to.
I find Luhmann's Zettelkasten method, as described in 'How to Take Smart Notes' more persuasive. As you read make bibliographic notes in your own words (on page X it says Y), store these in one place for everything you read. Also note down key ideas as you read with cross references to the bibliographic notes, and to other key idea notes that are relevant; store all these notes in another place. When you're filing a key idea have a look for similar ideas already noted; is this the same? Supporting? Contradictory? These questions help engage with the content. Over a lifetime you can amass a treasure chest of ideas that you can refer back to at your leisure, as Luhmann did.