Books can be take home, can be studied by the individual at their own pace. A student can create their own book because it is "real", "physical" and low tech.

Also, regarding books, there is, historically, a lot of content.

The same applies for Dynamicland.

For example: I learned how to use the graphics system in Realtalk with a physical booklet that I could have taken home and studied. The booklet had the code printed out on it, as well as hand written annotations from previous readers. The "magical" part was putting the booklet in a space running Realtalk and seeing live examples of the code projected onto each page as I flipped through the book.