I'll add all of Edward Tufte's books, which are excellent both in content and presentation. The Humane Interface by Jef Raskin was also formative for me.<p>They complement each other well; Raskin being more technologically/psychologically oriented and formal, while Tufte takes on information design in general at a higher level.<p>And I second The Design of Everyday Things by Don Norman, it should be required reading for anyone designing anything used by humans.