Continuing my odessy into UI design, I read Steve Krug's Don't Make Me Think. Like Spolsky's book, this one is a short, fast read, but don't understand that to mean the book is fatuous. There's plenty of good tips and concepts to be learned here. For instance, Krug's section on doing usability studies on the cheap is worth the cover price alone. Also of value was the "scan test", in which you ask someone to quickly identify key elements of your front page to see if things like navigation, section title and site utilities (e.g. login, search) are where users expect them to be.
If you're planning to build a web application, make this book apart of your permanent library.