Atomic Notes in a pile, not a hierarchy, linked to each other.
The Slip-Box Method (a.k.a. Zettelkasten Method) of notetaking was pioneered and made famous by a German sociologist named Niklas Luhmann. Rather than long, sprawling notes connected in a logical hierarchy, the method is centered around small notes, containing one thought, stored in a pile.
Luhmann’s notes were written on one side of a single notecard. These are Atomic Notes. They each contained one idea, and no more, and were tied together in a network via a branching indexing system. Each branch in the network represented a full train of thought, and it could extend indefinitely in any direction, forking and intersecting with other ideas and concepts along the way. All represented by short notes on individual notecards.
With this centralized repository of knowledge, you can read with a new sense of clarity. Notes you take on things you’re reading have a destined home. Because there’s already a rich collection of notes in that home, you can be more selective about the new notes you take. Only take notes if the add the conversation between you and your second brain.