Welcome to the developer documentation for Microsoft Dynamics CRM 2015 and Microsoft Dynamics CRM Online 2015 Update! You can read all the documentation online in the MSDN library or in the CHM file found in the download package. The download package also includes assemblies, developer tools, and a wide range of sample code and other resources. The download package is available here: Microsoft Dynamics CRM SDK.

http://msdn.microsoft.com/en-us/library/gg309408(v=crm.7).aspx