I got this book as a Christmas present and quickly read through it cover to cover. The primary focus of the book is to provide an introduction to LINQ (language integrated query) that is available in the Microsoft .NET Framework 3.5. In this end the book does a good job. Just don't look for anything comprehensive.
The book starts out talking about what LINQ is and follows that up with a few chapters that talk about the new language features in C# and VB that make LINQ possible. I found the information to give me a good understanding about how LINQ works if only at a very high level. However, these chapters take up about 20% of the book. I feel the author would have been better off shortening these chapters and adding more meat to other sections.
The syntax fundamentals follow the introduction. The chapter starts out good, but seems to become a regurgitation of product documentation towards the end. The fundamentals chapter is followed by chapters on the different flavors of LINQ that is LINQ to SQL, LINQ to Entities, etc. The one part of the book that I felt was really lacking is the LINQ to Entities section which was given a whopping three pages.
That all said, the book did a good job of getting me familiar with what the technology is and can do, and what options I have for using the technology in different areas. The information is based on the beta, and although I didn't look for differences I didn't run into any either. You could get the same information this book provides by reading the production documentation as well as several online articles on the subject of LINQ, but if you're like me you like it in one place in a convenient format to sit back and work through.
The list price on the book is way out there, but Amazon has it for a much more reasonable price of $23. I would recommend this book based on its ability to provide a good introduction keeping in mind that it doesn't offer advanced or in-depth coverage.