At 200 pages, this book is probably the best must-read book on creating usable web sites. Krug introduces all of the main concepts of usability, in what he calls "advanced common sense" language.

There are a lot of difference between web site usability and application usability... mainly because everybody uses web sites, so the audience is highly diverse, and they will leave your site for a better one relatively quickly. Usability has a lot to do with concise writing, intuitive structure, foolproof web forms, and the optimal blend of content and functionality. He covers many important topics including:

• how to write for the web
• the difference between usability testing and focus groups
• the fierce politics of the home page
• navigation structures that work well
• usability testing on a shoestring budget
• how to interpret test results

Even if you don't have the resources for a usability test -- in fact, especially if you don't -- you should get this book and follow his simple rules to make your web site ten times more usable.