
This book showed me how to design and write, from scratch, a real adventure game. How to design a game and draw maps (well, I was pretty accomplished at that already), how mazes worked, how to parse and handle the standard verb-noun input. Everything! I remember writing games and taking them (on cassette) to show my teacher at school. Awesome times.
[Edit: I've spent the last half hour looking, but no joy yet. It's not "Creating Adventure Games on Your Computer (Tim Hartnell) nor "Write Your Own Adventure Programs" (Jenny Tyler and Les Howarth)