Books work well for this since they have all the same verbal cues to aid your memory and understanding, but they also have physical cues to help you too. E-Readers don’t work as well for mental mapping because there are fewer tangible and stationary qualities to grasp at in organizing your mental map. The result is that books allow you to follow the whole course of an argument, like you are tracing the path on a map. Meanwhile, ebooks break the text into searchable snippets that don’t hang together as a whole text.