Software Development Kit
https://msdn.microsoft.com/en-US/library/hh547453(v=crm.8).aspx
Installation and Configuration Guide
https://technet.microsoft.com/en-US/library/hh699811(v=crm.8).aspx
Help Center with description of all the news features
https://www.microsoft.com/en-us/dynamics/crm-customer-center/what-s-new.aspx