Written by Bill Hughes and Indrajit Chakrabarty, is a good alternative introduction to the platform. From the back of the book:
Windows Phone 7 is a revolutionary mobile operating system that just begs for more creative ways to use its power. If you have an idea for a great mobile app or you've been considering getting into app development, this book is for you! Learn how to use Windows Phone developer tools to create your app, make it sparkle, and unveil it the world.
The right tools for the job — get to know Windows Phone 7, explore Visual Studio Express 2010, access the Microsoft Developer Portal, and play with Silverlight
Learn by doing — practice with some simple sample apps that help you learn the tools and see what goes into a great user experience
When it starts to be fun — learn to integrate motion and location information into your app
To market, to market — see that your app is correctly priced and categorized for best visibility
Remember the users — discover how regular updates and good customer support can boost sales
Anyone out there used these and can let everyone know how useful the content is?