This book this book starts with a great introduction to the windows phones. It introduces Metro design language, hardware specifications, input patterns, the application lifecycle, out of the box services, live tiles, and the marketplace. By the time you are done with the introduction you have a solid understanding of the windows phone context.
The book continues with ten more chapters. They include Writing Your First Phone Application, XAML Overview, Controls, Designing for the Phone, Developing for the Phone, Phone Integration, Databases and Storage, Multitasking, Services, and The Marketplace.
The author has a really nice writing style which makes the book an easy cover to cover read. It will also make a nice reference.
There are a bunch of tables, screenshots, and diagrams that really help explain the topic at hand. The author does not go overboard with them like some books I have seen that use them for filler.
One of the things I like about the book is that the author does a great job of switching between Visual Studio and Expression Blend at appropriate time. Not too many authors do that and I wish it was done more often. If you are developing with XAML, Blend needs to be part of the toolkit you master.
Another thing I like is the author shows you us how to take advantage of built in features like the camera, email, making a call, media player, and search.
The book also covers the Silverlight for Windows Phone Toolkit controls including AutoCompleteBox, ContextMenu, DatePicker, TimePicker, ListPicker, LongListSelector, PerformanceProgressBar, ToggleSwitch, ExpanderView, PhoneTextBox, and WrapPanel.
In chapter 7 the book covers all the integration tasks that are included with Windows Phone 7.1. It covers all the Launchers and all the Choosers.
The downloadable code is very well organized and usable.
All in all if you are considering Windows 7.5 development you owe it to yourself to get this book, digest it, and then keep it by your side.