Maybe the best example of puzzleless IF is Adam Cadre's Photopia. Instead of going through puzzles in the game (the old school Infocom way), the story is the puzzle which you unfold as you watch it happen from several angles. Photopia annoyed part of the IF community. Some claim this kind of storytelling is better accomplished by writing a short story rather than a game. Interactivity is hurt in Photopia (you can't branch the story) but still this is one great example of the path IF is following today, as it becomes less of a media for games and more of a media for interactive art.