1. I don't take notes on every book I read.
If a book isn't good enough, I don't take notes. I also generally don't take notes for fiction books or entertaining non-fiction.
2. When I do take notes, their depth and breadth varies.
I focus on the parts that I'm most interested in/are relevant to me. This means that my notes are not a complete representation of the book. The amount of detail in my notes is informed by how valuable I think an idea is.