It's taken a long time for critics to realise that some of the finest writing in the world is - and always has been - fantasy literature, and that it takes many forms, from, say, John Crowley's 'Little, Big' to Natsume Soseki's 'I Am A Cat'. But how do you attract the right readership? It's easy to see the demographic strategy behind cover art, and to dismiss a great many authors on the strength…