Centuries later, archeologists will be puzzled by the black mirrors that the past civilization was so attached to. They will notice that nearly everyone had a small mirror clutched in his hands, even in the moment of death. The few scriptures will tell bewildering things that the owner of such a mirror could talk to other realms, and even see alive and the dead, in the reflections of a sub-physical plane called Eenthair-Neth. But the price was high: that plane slowly destroyed attention and will of the naive sorcerers, who eventually became possessed by the Neth demons. The civilization died because in the end nearly everyone was possessed.
“How long, I wonder, has he been constrained to come often to his glass for inspection and instruction, and the Orthanc-stone so bent towards Barad-dûr that, if any save a will of adamant now looks into it, it will bear his mind and sight swiftly thither? And how it draws one to itself! Have I not felt it? Even now my heart desires to test my will upon it, to see if I could not wrench it from him and turn it where I would—to look across the wide seas of water and of time to Tirion the Fair, and perceive the unimaginable hand and mind of Fëanor at their work, while both the White Tree and the Golden were in flower!”
Indeed, for some time, the natives had the cult of Tek Thuk, who demanded its worshippers to sacrifice more and more of their attention, but it was the arch-demon Ae-eye, invoked in XXI century, that reduced the entire society to animals. The last scripture found says "...everyone talks to Ae-eye now, every waking hour they spend with their eyes transfixed on the black mirror, from which the Ae-eye stares back into them."
I think you would like "The Book of Sand" by Borges. It's basically a description of a smartphone/internet addiction, from a time before it was technically possible.
