Please enjoy the following usability resources.
The Elements of User Experience: User-Centered Design for the Web, by Jesse James Garrett (New Riders, 2002, ISBN: 0735712026).
Don't Make Me Think: A Common Sense Approach to Web Usability, by Steve Krug (New Riders, 2000, ISBN: 0789723107).
Designing Web Usability: The Practice of Simplicity, by Jakob Nielsen (New Riders, 1999, ISBN: 156205810X).
Homepage Usability: 50 Websites Deconstructed, by Jakob Nielsen and Marie Tahir (New Riders, 2001, ISBN: 073571102X).