I have been working on developing a web application now for about 6 months and just recently got this book. I only wish I had got hold of it 6 months ago. Looking through the table of contents it contains examples of nearly all the Javascript functionality that I have struggled to incorporate into our application. I would have saved loads of time and probably have coded things a lot more efficiently if I'd had this book first. Topics such as date validation, handling script errors, creating a new window, bringing a window to the front, changing the contents of one frame from another, resizing frames, setting frameset specifications dynamically, blocking submissions from the Enter Key, Advancing Text Field Focus with the Enter Key to name just a few! I've already used it since getting it to look up modal windows and creating tree-view structures.
This is everything I expected that book to be.
I heartily recommend this book. It has tons of highly usable examples.