I highly recommend The Design of Everyday Things to everyone I know who is designing any kind of user interface, whether machinery, houses, or software.

I believe that until there is some effective, easy, and universally-accepted metric of UI quality, there will be little to differentiate good designers from poor. ("Our UI meets UIQC Class 1 Standards", or in a specification, "All user screens must score level 96 or better on the UIQC test", or some such thing.)