Physical books are better than “licensed e-reader material”. Let me explain why.
The invisible hand of Amazon can’t reach in and change or destroy your books. You can lend them, sell them, or give them away. They smell good. If you happen to misplace one, you didn’t lose a $200 piece of equipment. A lot of people want to steal your e-reader, but nobody wants to steal your book. Books do not need batteries, electricity, or any other hallmarks of civilization. Books will survive the next fall of civilization. You can borrow books from a public library, and it does not cost money.
When you read a book you are an icon of literacy, intelligence, and introspection; but holding an e-reader makes you look like a self-indulgent bandwagon-hopper. My grandparents read books, my parents read books, and I will read books.