Animal Farm by George Orwell (1945)

On a barn wall, a single law is painted that the animals can read by heart, and over the seasons a word is quietly added in the night, then another, until the law means its own opposite. Orwell called this small book a fairy story, and it has the clean cruelty of one. The beasts of Manor Farm rise up, drive out their drunken master, and swear that no creature shall ever again live under the boot, only to watch the pigs who led them swell into the very thing they overthrew. The heartbreak is Boxer, the great cart-horse whose answer to every hardship is that he will work harder, and who is sold to the knacker for a case of whisky the day his strength gives out. By the last page the others crowd to the farmhouse window, looking from pig to man and man to pig, and finding they can no longer tell which is which.