Books, especially textbooks, would be amazing. These things can get pretty huge (1000+ pages) and usually do not fit into GPT-4o or Claude Sonnet 3.5 in my experience. I envision the models being able to help a user (student) create their study guides and quizzes, based on ingesting the entire book. Given the ability to ingest an entire book, I imagine a model could plan how and when to introduce each concept in the textbook better than a model only a part of the textbook.