If you are looking for free eBooks for Windows 7, Windows 8, the Microsoft Office 2013, the Office 365, or Azure, Microsoft just released 130 free eBooks that provide information relevant to most of the products her.
Eric Ligman, Microsoft Corporation's senior sales manager, told the MSDN blog that these e-books will be distributed free of charge and that we all have to have them.
Most books are available in three different formats, namely ePub, MOBI, and PDF, and almost all contain at least one version PDF.
You can view and download books from here.