Jakob Nielsen is a leading world expert on how to make websites truly usable, and his Alertboxemail newsletter has helped many web designers to understand these issues. This book looks at the mistakes – and good points – of some leading websites. It shows us examples to follow, and faults to avoid. Although it was published several years ago, and graphic styles have changed since then, usability issues remain relatively unchanged.
If you are interested in full-blown website usability testing, Nielsen’s 159 page report Eyetracking Methodology – 65 Guidelines for How to Conduct and Evaluate Usability Studies Using Eyetracking as a free 16Mb PDF ebook.
See also Nielsen’s many online articles, reports and book recommendations (and sign up for the free Alertbox newsletter) at UseIt.com.