A favourite mathematical subject of science-fiction writers has produced enough stories to define a genre: topological fiction, where ‘toopology’ refers to the study of continuous deformation of shapes in space. Robert Heinlein’s ‘And He Built a Crooked House,’ published in 1940.The writers have set stories in frankly imaginary worlds for the sake of unusual topological structures of space, but few have been so careful to define the structures as Heinlein was. It is common