If you think a book is made by the physical medium, you must think everything in paper is a book. The prose in a book has certain content structure, intent, and

If you think a book is made by the physical medium, you must think everything in paper is a book. The prose in a book has certain content structure, intent, and writing. So unless a napkin and a receipt are books, what actually makes something a book is its content structure, intent, and writing. Not the paper it's printed on.