Perhaps my favorite Windows Phone book ( after SAMS Windows Phone 7.5 Development in 24 Hours, of course ) was Andrew Whitechapel’s Windows Phone 7 Development Internals.  The book offered a great inside look at almost all the phone internals.  Andrew’s book turned into a referral / goto reference for items we weren’t able to get to in our SAMs book when I was coaching people on their WP75 development.

I’m happy to relay that the ebook preview of his book for Windows Phone 8 is available on the OReilly site.  If you purchase it right now, its $20.00.  By the time it finally publishes it will be a $60 book, but you’re getting in early and will be able to download the full book at the end.  Charles Petzold used this model recently for his Programming Windows Sixth Edition ( Windows 8 ) book. 

Save some money, buy the book early.  Current chapters include Vision and Architecture, App Model and Navigation, Data Binding and MVVM, Tiles and Notifications, Location and Maps, and Speech.  Enjoy…

Purchase through OReilly here - http://shop.oreilly.com/product/0790145373342.do