A Mind Forever Voyaging

First of all, I'm biased, because this kind of story is right up my alley. I regard it as my all-time favorite because the story is masterfully written, the descriptions are robust and entertaining to read and overall, it makes you think, not so much about the puzzles, but about what is happening, both to your character and to the world around him. As Infocom stories go, this will remain one of the tops in my book.