Manifold Sky

• Flatland (Edwin A. Abbot): A Romance of Many Dimensions - a piece of mathematical fiction layered with interesting worldbuilding and incisive social commentary about people's inability to accept that which challenges their presuppositions about the world.
• Neuromancer (William Gibson) - Seminal work of the -punk genres.
• The Difference Engine (Bruce Sterling & William Gibson) - Seminal work of the steampunk genre.
• The Call of Cthulhu (H.P. Lovecraft) - Weird fiction story involving alien beings, non-Euclidean geometries, and dimensions that regular human beings cannot perceive.

Without knowing what futurism is like, Johansen achieved something very close to it when he spoke of the city; for instead of describing any definite structure or building, he dwells only on broad impressions of vast angles and stone surfaces—surfaces too great to belong to any thing right or proper for this earth, and impious with horrible images and hieroglyphs. I mention his talk about angles because it suggests something Wilcox had told me of his awful dreams. He had said that the geometry of the dream-place he saw was abnormal, non-Euclidean, and loathsomely redolent of spheres and dimensions apart from ours.

— H.P. Lovecraft, The Call of Cthulhu

I have told you I can see from my position in Space the inside of all things that you consider closed. For example, I see in yonder cupboard near which you are standing, several of what you call boxes (but like everything else in Flatland, they have no tops nor bottoms) full of money; I see also two tablets of accounts. I am about to descend into that cupboard and to bring you one of those tablets. I saw you lock the cupboard half an hour ago, and I know you have the key in your possession. But I descend from Space; the doors, you see, remain unmoved. Now I am in the cupboard and am taking the tablet. Now I have it. Now I ascend with it. I rushed to the closet and dashed the door open. One of the tablets was gone. With a mocking laugh, the Stranger appeared in the other corner of the room, and at the same time the tablet appeared upon the floor. I took it up. There could be no doubt—it was the missing tablet. I groaned with horror, doubting whether I was not out of my senses; but the Stranger continued: "Surely you must now see that my explanation, and no other, suits the phenomena. What you call Solid things are really superficial; what you call Space is really nothing but a great Plane. I am in Space, and look down upon the insides of the things of which you only see the outsides. You could leave this Plane yourself, if you could but summon up the necessary volition. A slight upward or downward motion would enable you to see all that I can see.

— Edwin A. Abbott, Flatland: A Romance of Many Dimensions