The Windows Phone Blue Book Mango Version is now available. This is for Version 7.5 (Mango) of the phone and 7.1 of the tools.
You can download it from here.
The file is quite big, around 130M. This is because you don't just get the book, you also get a complete course including sample code, Powerpoint decks and labs.
Important: When you unzip the files there are some quite long file paths in the sample code. This is because a Windows Phone project can have quite a few subfolders beneath it. You can avoid this problem by unzipping to somewhere quite high up the directory hierarchy on your disk, perhaps c:\WP7 for example.