FEERSUM ENDJINN was published in 1994
It is science fiction, but not Culture

Count Sessine is about to die for the very last time…
Chief Scientist Gadfium is about to receive the mysterious message she has been waiting for from the Plain of Sliding Stones…
And Bascule the Teller, in search of an ant, is about to enter the chaos of the crypt...
And everything is about to change...for this is the time of the Encroachment and, although the dimming sun still shines on the vast, towering walls of Serehfa Fastness, the end is close at hand.
The King knows it, his closest advisers know it, yet still they prosecute the war against the clan Engineers with increasing savagery.
The crypt knows it too; so an emissary has been sent, an emissary who holds the key to all their futures.

Iain said, “I had wanted to write something I could cut loose on, something that wasn’t the Culture...I liked the exotic feel of Against a Dark Background and wanted to do something like that on Earth. I thought the big structures in Against a Dark Background hadn’t been big enough, so I came up with the mega castle which was originally a space elevator. I also had the idea that what virtual reality would become eventually would start to resemble myth and legend. I wanted to use different voices as well.”
Responding to a fan letter, Iain wrote, “I’m glad you liked Feersum [Endjinn] - I enjoyed doing the Bascule bits most and it was frighteningly easy to write them2; @ times I stil okayzhinily fynd myself sliping in2 Bascule-speke. Oh, at the end, the Endjinn is the sun; it moves the whole Solar System out of the way of the Encroachment. I mean, like, hey; it’s the obvious thing when you think about it.”