At a basic level, becoming smarter than your previous self means that you learn something you didn’t previously know. By reading and then continuing to read, you do this over and over. Some things will stick. Some will not. Over time, you’ll rake in new practical information and use it to communicate better and analyze better in real life. Even if you stick strictly to fantasy books, you’re going to get smarter. But of course, if smarter is your goal, nonfiction books are about as practical as they come.