DOET (neé Psychology of Everyday Things) deeply influenced me. Articulated things I had observed, experienced. Expanded my thinking.

I was using, teaching, and developing for AutoCAD at the time. Knew nothing about UI beyond my intuition. Just perplexed by how difficult it was for most to use.

Reflecting back, Norman's treatment of mental models and kinds of errors were the most impactful, evergreen design challenges I faced.