Since many years, Microsoft is delivering more and more free ebooks resources.
An updated list has been published, covering Windows 8/2012, SharePoint or Office 365 as well as Visual Studio or Windows Azure
Feel free to pick the one(s) you want 
http://blogs.msdn.com/b/mssmallbiz/archive/2013/06/18/huge-collection-of-free-microsoft-ebooks-for-you-including-office-office-365-sharepoint-sql-server-system-center-visual-studio-web-development-windows-windows-azure-and-windows-server.aspx