Mind Mapping is a visual modelling concept where related ideas and tasks are arranged around a central idea.
I often come across people talking about using mindmaps for the books they read. It makes more sense for non fiction books of course, and is a great way to summarize the book. The summarization can be done to any level of detail - the more fine grained you are, the more nodes your mind map will have.
I tried it on a book I read recently - Edward Luce's In Spite of the Gods. I did not have the patience to go to a very fine level of detail, so it's very very brief. Nevertheless, creating one is a good way to keep the central ideas of the book in focus.
