Others say...

"Web 2.0 Tips & Tricks"
This book explains the techniques behind the DropThings portal [...] showing some source-code (available at www.codeplex.com) and giving a couple of tips and tricks of web 2.0 programming. The book is very interesting but it's for those developers who already know the technologies it covers (ASP.NET, C#, LINQ, WF and ASP.NET AJAX) and want to know "the best way to do it" or became aware of commom problems that big web 2.0 portals generally has.
Below is the main topics of each chapter:

Chapter 1 - Conceptual meanings of Web and ASP.NET.
Chapter 2 - How can you design your own Widgets Framework (Based on his ideas that lead him to develop his own framework) and things that you need to concern when you develop a big portal.
Chapter 3 - Tips and Tricks of developing rich client controls
Chapter 4 - How can you add LINQ and Workflow Foundation to your Data and Business Layers.
Chapter 5 - Developing Widgets itself
Chapter 6, 7, 8 and 9 - Reflections over performance (at Client, Server and "client-server" interaction)
Chapter 10 - Solving Deployment and "Go-live" problems.

Bear in mind this book don't teach you those technologies, it only leads you to use them in a better way based on the author's experience (Author is the PageFlake's co-Founder and CTO, so he really knows what he's talking about).

In conclusion, if you want to learn how you use those technologies (Asp.net Ajax, Workflow Foundation..), I recommend you to try other books. Otherwise, if you want to know more about how to create a scalable web 2.0 site, tips & tricks and the best practices of those techs at web, this book will hit at the bullseye.

"Lots of good tips"
I would say this is a better "Tips" book than a cookbook. If you are just starting out with this technology, you'll need to fill in a lot of details. But there's a lot of good work here.

"Great Book"
Omar is an excellent .NET programmer and I really enjoyed his book. This book gave excellent insight on running a high volume website with ASP.NET. It also dives into some of the new features of the .NET 3.5 framework. I really enjoyed the sections towards the end where he showed the type of hosting environment necessary to run a large scale website. I would also recommend subscribing to Omar's RSS feeds for excellent tips.

"A must have resource for all ASP.NET developers!"
I've read the author's articles on Code Project, and when I found out he had written a book that built on them, I didn't waste any time getting my hands on it!

Being the one of the few developers in my group that work with the latest "cutting edge" technology, and with no one to answer the questions I have, this book has simply been the fountain of knowledge I'd been looking for. Definitely a must-read for those wishing to utilize the latest and greatest.

The book is well organized, and the writing style makes it an easy read (usually technical books put me to sleep, but not this one). It does assume that you've already had some experience using ASP.NET 2.0/3.5, Javascript, and so forth, so I agree that this book will be the most beneficial to seasoned and advanced ASP.NET developers.