— Start by reading "Designing with the mind in mind" by Jeff Johnson (http://www.amazon.com/Designing-Mind-Simple-Understanding-In...)
— Now you understand that UX design is actually cognitive psychology + sociology. Of course, most cognitive psychology/sociology books will only be slightly relevant to UX design. Here's a short selection to get you started:
— Don Norman, Design of Everyday Objects
— Don Norman, Emotional Design
— Brenda Laurel, Computers as Theater
— Kim Goodwin, Designing for the Digital Age: How to Create Human-Centered Products and Servicesa
— Bill Moggridge, Designing Interactions
— Raph Koster, A Theory of Fun for Game Design (meant for video game design, but has a lot of lessons that can be applied to good UX)
For UI design, I'd also heavily recommend "Semiology of Graphics: Diagrams, Networks, Maps" by Jacques Bertin, and anything by Tufte. These titles are more about data visualization, but most UIs need a way to visualize data in some shape or form.
One point that msutherl forgot in his fantastic comment is animation (as in, 2D animation). UIs are not static things, and animators have spent decades understanding how we react emotionally to animations (Good introductory read: http://labs.oracle.com/techrep/1995/smli_tr-95-33.pdf). Good animation in a UI makes a whole lot of difference— Apple knows that (http://watchingapple.com/2007/06/are-apple-ui-designers-lear...).
For this, only one resource: "The Animator's Survival Kit", by Richard Williams.
Excited to check out some of the stuff I haven't come across there.