It's really gelled if you can talk about the book 2 days after closing it. The memory will have forgotten as much as 80% of what you read (and learn) if you don't use it or do something to remember it. The layering as you learn helps the retention.
The fact that you need to look at your notes means you're not particularly interested in the subject or haven't worked out a use for it. If you're able to call up information easily it is because it's connected to something interesting to you.
Subject for school usually fall in the category, "what's the point?" Failing to answer that you lack curiosity and interest so you need alternative methods to bring the memory into play.
If you're studying you have to work with the memory curve. If you want long term memory of what you learned Review it daily for a week. Then once a week for a month then once a month for six months and then once annually, though most people will find they are actively using the information in their career or it's redundant to their needs by that point.
The ease of reviewing mind maps 90 seconds to 3 minutes is usually enough and more useful than notes. Also mind mapping if you're being playful while creating the branches, helps to introduce interest that is often lacking in compulsory classroom subjects.
Alex
