Things you can't do with a book (though I still love them): tap words to get a definition; carry thousands in your back pocket; highlight text non-destructively

Things you can't do with a book (though I still love them): tap words to get a definition; carry thousands in your back pocket; highlight text non-destructively; write notes non-destructively; change the font size; read in the dark; know how long until you finish the chapter/book ....