I love gushing about this book, so just to give people a taste of how meta this book gets (and because I'm pretty sure nobody here is actually going to read this book far enough to see these plot points), allow me to spoil some things for you:

>!So this isn't actually about someone realizing they're inside a book. This is a book about someone reading a book about someone else who's realizing they're in a book. To keep things straight, I'll use names.!<

>!Hilda is reading a book about philosophy that was written by her father (who we'll call "the author"), and it was written explicitly for Hilda. In the book, a girl named Sophie is taught philosophy by a mysterious man named Alberto. Halfway through the story, Alberto reveals to Sophie that they are both inside Hilda's book. Alberto has known the whole time, but he didn't want to tell Sophie because then Hilda would also find out.!<

>!Once Sophie (and by proxy, Hilda (and by proxy, us as readers)) find out that Sophie's world isn't real, the author drops all pretenses. Fairy tale creatures appear and strange phenomena just happen, because the author knows he doesn't need to justify it anymore. Sophie and Alberto start trying to figure out which parts of their lives are part of Hilda's book and which parts were skipped over, so they can start plotting against the author to escape the book. As the story nears the end, the author has to make things happen faster and faster, to avoid any kind of time skip and prevent Sophie and Alberto from having time "off-camera". Hilda at one point wonders if she can give S&A some privacy by skipping past a few pages.!<

>!The point of the book, though, is that Hilda repeatedly wonders to herself whether or not she is real or fictional. She realizes at one point that there's nothing she can do to prove to herself that she is real (because of course she isn't - we as readers know she is indeed a character in a book). Which then prompts the question: how do we know that we're real? What if we are also just a character in someone else's book? And if we are just characters in a book, how should we react to that information?!<