

OK, I’ll go all-in on this:
2000 AD Comics’ Nexus, The computer game.
Made for the Commodore C128 computer (which oddly ran Microsoft Basic), it was a simple single-screen platform shooter with the twist that you could pile up the bodies of your enemies and use them as platforms.

The Zombie Survival Guide by Max Brookes is a detailed fictional instruction manual. It’s sequel is World War Z which is closer to a normal book, but still has an odd structure of creating a world through interviews … and the The Zombie Survival Guide book exists within it.