“The Design of Everyday Things” by Don Norman is excellent; he originally called it “The Psychology of Everyday Things,” but it kept getting misshelved. “Don’t Make Me Think” by Steve Krug is also very good. Neither of these is a specialist’s tome.

“Mental Models” by Indi Young is good, one level deeper, mostly about humans. “About Face” by Alan Cooper is very thorough on the practitioner side, more of a college textbook, with lots of examples and pedagogy.