Gryffindor, Slytherin, Hufflepuff, Ravenclaw ... Twenty years ago these magical words and many more flowed from a young writer's pen, an orphan called Harry Potter was freed from the cupboard under the stairs - and a global phenomenon started. Harry Potter and the Philosopher's Stone has been read and loved by every new generation since. To mark the 20th anniversary of first publication, Bloomsbury has published four House Editions of J.K. Rowling's modern classic.