To properly grok new information you need to actively engage with it and for material that you're reading this can be achieved by doing multiple levels of processing on it. Common suggested levels include
Taking fleeting notes about the material while you're in the process of reading it highlighting works too in a pinch, but it's worse, as the level of engagement is lower
Look over your fleeting notes and identify the ones that are worth elaboration
Synthesized the insight from the chosen fleeting notes into Evergreen by translating them into your thinking context and elaborating them evergreen notes are the ideas or a thoughts elaborated in their full form
Another level of processing, in a way, is apply Spaced Repetition to evergreen notes that you want to remember or periodically rise to attention. I've been applying this to first level of processing mostly so far. But this is something that can be developed further, I feel like I haven't discovered it's full potential yet.
This seems like one of the key ideas of zettelkasten, Progressive Summarization How to Read a Book