I switched to e-books 12+ years ago, and I can't read regular books anymore. First, I need to find really good light (like direct sun light on a sunny day). Otherwise my eyes become tired quickly. Second, the book has to have a good paper quality (cheap greyish paper diminishes contrast). Third, the font should be large enough again not to strain the eyes. Fourth, regular book is heavier, I can't hold it with one hand, so end up sitting in uncomfortable positions (hello lumbar back pain, fellow readers). Fifth, I have utmost respect to paper books (parents had a library, so I grew up between books), and I have to wash my hands and dry them perfectly before I touch a paper book. I don't feel comfortable eating a croissant and read a paper book.
Not to mention that it's just not always possible to find or buy book you want, especially in a reasonable time.
Paper books are also screens in a way. Just with a user-controlled refresh rate (turn the page), and predefined images.