Plans and Situated Actions: The Problem of Human-Machine Communication and Dynamics in Document Design: Creating Text for Readers have been recommended to me by students in a class called "Communication Design for the WWW" at Rensselaer Polytechnic Institute. Their professor, Bill Hart-Davidson, writes of the dynamics book "...also serious reading, but well worth it. I've heard it called the "Tufte of Document Design," which isn't far off."

The Social Life of Information Okay, I haven't read it, but it's a to-do. Decide for yourself. (and if you have read it, please comment on it!)