How about Tog on Interface - Bruce Tognazzini at http://www.asktog.com/
This is old now - and completely Apple-centric - but when it comes to understanding UI design principles, it’s still one of the books that influenced me the most. His discussion of how in the old days Apple tried to work out how to get users to figure out during installation of a software package whether they had a colour or monochrome screen is a classic example of how some problems are just about intractably difficult, and how users will make rational decisions (to them) that are absolutely NOT what developers anticipated. And his ‘hotel lobby’ cartoon is absolutely classic!. A great book if you can find a copy.