Hamlet is a good example of the non-primacy of books. Hamlet was meant to be performed, not read silently. It's far better to have access to a recording or taped performance to study it than the text alone. And yes, a plot summary or additional commentaries could be a big help as well. In our current information golden age I can pull up a dozen full performances on YouTube including a 360 degree VR experience where you can stand on stage with the actors. In 1990 such a thing would have been pure science fiction and you would have never encountered a person to even discuss the topic of serious Shakespearian study.