Curses is the first game I think of when I think of interactive fiction, together with Anchorhead. Sprawling, light-hearted, with a compelling backstory and cast of supporting characters.
For me, the beauty of the game is in the development of the plot, with a continually increasing sense of wonder. Another wonderful aspect is the open sandbox feel; this is a very non-linear game.
Although the game is very difficult (I've played through it three times, and had to resort to a walkthrough every time), there are so many puzzles that you will still solve quite a few on your own. Many puzzles have multiple solutions, or can be bypassed completely.
*Amusing things: There are three characters that have interesting reactions to all ten of the (Spoiler - click to show)rods. Those characters are (Spoiler - click to show)yourself, the knight, and Austin.