This book is about using .NET technologies to work with data. Since data can reside in different forms at different places, this book focuses on; databases, XML/XSL, directory services and files.
If you are a programmer with extensive experience with C# and ADO.NET this book might not be very helpful. However, if you' are doing database programming with .NET and still learning ADO.NET and C#, then this book is a very good choice.
It has a good spectrum of coverage and is really for those applying C# and .Net to a real world situation. It is not going to teach you syntax for C# but will show you how to use the .NET framework for Data intensive apps using technologies such as XML and Active Directory. In addition it discusses how to migrate existing apps over to .NET.
All in all this is a very good book. I would give this book 8/10 points and recommend it to any developer seriously interested in .NET C# programming.
A word of warning - this book has been written with the Beta 2 version.