Showed up in my MSDN newsletter. Offer good through August 27 (tomorrow).
https://www.microsoftelearning.com/e...enterCode.aspx
A valid Windows Live ID is required. The access code is 7234-N4E8-4995.
It's in PDF format. You can download individual chapters or the whole book. There must not be any DRM on it because I downloaded and viewed within Linux.