An interesting way to think about note taking: the CODE concept from Tiago Forte.
CODE stands for capture, organize, distill and express.
Capture refers to saving the ideas and insights worth saving. That is, not the whole book you’re reading, but the really important themes and concepts that resonate with your work.
Organize is self-explanatory, although here Forte suggests you use the PARA method for organizing what you capture.
Distilling is processing your notes into actionable or otherwise useful summaries. Of particular importance here is designing notes for your future self. You have to make them clear enough and detailed enough to be valuable long after you’ve forgotten the original book or article you were reading.
Finally expressing yourself: actually putting the notes to use, and creating something out of the knowledge you’ve collected. Like the essay I wrote: The grey goo scenario is happening.