Download the documents here
- Application Development Guide
The OEM and MO Application Guide for WP7 provides guidance on developing applications for a Windows Phone.
- WP7 Architecture Guide
The Architecture Guide provides fundamental technical information about WP7. It serves as a roadmap to the components and core fundamentals of the WP7 architecture.
- WP7 Customization Guide
The Customization Guide for WP7 provides information about customizing the user interface and other system functionality.
Have fun reading, thanks to Tom Codon.