Photopia

This is a work so hugely influential to IF development that anyone interested in the history of the form should try it: it experiments with non-linear presentation of time, menu-based conversation, and constrained game-play to support a specific plot. A number of its features look perfectly ordinary now, but were ground-breaking at the time. Photopia's particular form of menu conversation, for instance, was spun off into a library used in a number of other works.

How well does it work, beyond that? Opinions vary. Some people consider it the most moving piece of IF they've ever tried. I personally found it wavered between effective and manipulative, with the main character too saintly to be true. While it was worth playing, it is by no means my favorite piece of character-oriented IF story-telling.