NOTE: This book has been updated for Windows Phone 8. You can buy it here from The Microsoft Press Store.
Each chapter covers a set of related features. For each feature, the book provides one or more sample applications, and walks you through the significant code (C# and XAML), so you can understand both the techniques and the design and implementation choices that you have in each case. The book calls out potential pitfalls and provides scenarios where you can typically make performance or user experience improvements. An underlying theme of the book is not only to conform to the UI design guidelines, but to also to the notion of a balanced, healthy phone ecosystem.
This book is scheduled to be available in print and e formats in just a few short weeks in June, 2012.