I chose this book to assist me with getting up to speed with Blend as a visual design tool for our development work.. Having been a Windows Forms developer using Visual Studio for many years, I have the need to develop some applications using WPF and Silverlight, as well as for Windows Phone 7, and therefore have chosen to utilise Blend. This book was a great guide in introducing Blend as the tool for the job.
This book does not teach you XAML, nor is that its purpose, it just concentrates on Blend as an application, running through its many functions and options. It does this well, going through the interface stage by stage, this allows the book to be used as a quick reference in future if you need to concentrate on a specific area. The whole book is printed in colour which is a very nice touch, not only does it make the pictures/screen shots much clearer to understand (and this book has a lot of pictures which is great), but it makes the examples much more legible.
For me, as an existing developer who needed to get an introduction to Blend and make good use of it, this book was ideal and I would recommend it.