Magic Ink: Information Software and the Graphical Interface (2006)

I recently discovered this five-year old essay by Bret Victor who, coincidentally, has another article on the front page right now (http://news.ycombinator.com/item?id=3212949). It discusses how to improve user interfaces by focusing less on interaction and more on information/graphic design.

It's long but worth your time. If nothing else, have a look at the proposed redesign of Amazon search results, and the hypothetical flight planning website that looks eerily similar to Hipmunk's eventual design.