Turbo, have a look here
Mike Singleton, the author of Midwinter, had previously written two of the best Spectrum games (Lords of Midnight and Doomdark's Revenger). He always tried to create vast and densely populated worlds with interesting emergent behaviours combining storyline, character interactions and strategy. He's kind of a legend in the Speccy world at least.
My personal favorite has to be the Diary of a Madman that came with the game Dreamweb for the Amiga. If you haven't read it, you owe it to yourself to grab a copy now. The game kicked ass (if you're into this kind of thing as usual).
There are many, many others I could mention but somehow these seem to stand out in my mind.
I still think the book that came with the original release of Elite was also truly amazing btw. You can read it here.