Learning Windows Phone Programming - Preview Chapters

If you are getting started with Windows Phone 7 development, you can check two preview chapters from the book Learning Windows Phone Programming being written by two Microsoft folks Yochay Kiriaty and Jaime Rodriguez. On the book's dedicated website, the authors specify their objective -
"Our goal for the book is to share an insider view into Windows Phone. We want to share the insights from the product team, and lessons learned from the very early adopters."

The site also has a Windows Phone FAQ that has links to two other FAQ compilations.

Also see:
What's in Windows Phone 7 for Developers
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