For a limited time, and for a limited readership this book is as good as you will get.
Now, unless I have things badly wrong this book has a serious problem, unless you are an MSDN subscriber you can only read it. Without being able to try out the code and experiment with it, the book looses a great deal of its value. It is easy to read the specifications of a language but getting you mind round it means that you must get your hands dirty by trying a bit o coding.
Of course, as a journalist I could go and nag Microsoft for a copy of the beta software (well I probably will anyway) but that would miss the point. This book is likely to be bought by enthusiasts who then find that the have no easy legal access to the software that the authors have based their work on. Note the description that this book is based on a public Beta, if it really is public why did they not arrange for a CD copy with the book. Yes the authors do say you will need to get a copy and that you can get that free if you are an MSDN subscriber or on CD for a nominal charge, but readers are likely to see this too late.
If you have access to the relevant software, this book will get you started with using it, if you do not, then leave the book on the shelf. If Microsoft really want C# to become popular, they need to make it a little more accessible.
An added feature of this book is that it will have a relatively short shelf life, as soon as C# goes to release, books that deal with the final language will be the way to go.
For a limited time, and for a limited readership this book is as good as you will get. By the end of the year, I expect better alternatives to be available. I know that I have studiously avoided actually reviewing this book, but I do not expect it to still be around in a year's time.