D, While I agree with you, at first glance, this might seem like an all encompassing list of books but it really is the essential list of books.  I'll take the JavaScript/jQuery books for example.

JavaScript: The Definitive Guide is really a reference book.  You look through it when you first get it to familiarize yourself with it's contents then it should sit next to you when you need to look something up.

JavaScript: The Good Parts - if you are writing JavaScript and haven't read this book you're probably doing it wrong.  It's such a short book too but it is invaluable to developers understand the good standards that JavaScript offers and allows you to develop using those best practices.  Douglas Crockford is the godfather of JavaScript and thus his word is holy which makes this book the bible.

Pro JavaScript Techniques - Written by John Resig, creator of the jQuery JavaScript Library.  This book was one of the first JavaScript books to come out and really does a great job of laying out JavaScript in terms you can understand.  Again learning JavaScript from someone as smart as John makes this ESSENTIAL.

Secrets of the JavaScript Ninja - Again written by John Resig is one of the books that will elevate your development skills in JavaScript.  Once you think you knew everything in JavaScript Development this book will open your eyes again.  I wouldn't consider this an essential book right away but if you're looking to take your skills to the next level then this book becomes essential.

jQuery Cookbook - This is just duh essential.  Learn jQuery from those that are closest to the development of jQuery.  From jQuery team members to Professional jQuery Developers this book was written by 19 jQuery Community members.  Gain their knowledge in bit sized recipies on almost every problem you might face while writing jQuery and jQuery UI. (Disclaimer: I've written Chapter 3: Beyond the Basics of this book)

Learning jQuery 1.3 &amp; Learning jQuery 1.4 (the update to 1.3) - This is one of the top selling books on jQuery and it really does a great job of teaching you jQuery.

jQuery Enlightenment - you've never seen a jQuery e-book like this.  It's direct and to the point and allows you to play with the code example with a click of a link as they are all hosted on jsbin.com.  jsbin.com allows you to edit the source and play and learn from a starting point.  

jQuery in Action - Alot of books tell you how to do something simple.  jQuery in Action gives you the big picture on developing applications with jQuery.  In the second addition they expand and show you how to build applications using jQuery UI.  Learn the best practices from jQuery Team Member Yehuda Katz who is crazy smart when it comes to development.

jQuery: Novice to Ninja - I love this book because it wasn't written by authors that really close to the team or project. So you get an outside looking in approach to jQuery Development which is great in my opinion.  I feel this book is essential to jQuery Development but could easily be substituted for jQuery in Action or Learning jQuery 1.x

Looking over the other books I would say Introducing HTML5 will be a foregone conclusion to be essential due to the authors.  Remy Sharp is a blogger that helps with articles on html5doctor.com and is a respected developer, speaker, author in HTML5.

Steven Souders and Nicholas Zakas are on the front lines on sites like Google and Yahoo.  They understand high traffic sites and have the research and experience to make your site more efficient which makes High Performance Web Sites, Even Faster Web Sites and High Performance JavaScript the must have books on the subject.  

Finally,  Designing with Progressive Enhancement  written by the Filament Group who are leading the way in UI and user experience. They are the group that is at the forefront of jQuery UI and what they say about user experience and providing fallback to older browsers using techniques like Progressive Enhancement is why this is an essential book.

I hope this helped.  You obviously don't have to buy every book but I would feel confident in the recommendations in the books Rey listed here would have the content you'll need to gain the knowledge you require.

Ralph Whitbeck

PS. Both Rey and I are cohosts on the Official jQuery Podcast and we've interviewed many of these authors for the books that we list on episodes on our show.