It’s all in Hogwarts, A History. Though, of course, that book’s not entirely reliable. A Revised History of Hogwarts would be a more accurate title. Or A Highly Biased and Selective History of Hogwarts, Which Glosses Over the Nastier Aspects of the School.” “What are you on about?” said Ron, though Harry thought he knew what was coming. “House-elves!” said Hermione, her eyes flashing. “Not once, in over a thousand pages, does Hogwarts, A History mention that we are all colluding in the oppression of a hundred slaves!