If you want to know a ton of spoilerific information regarding The Witcher 3: Wild Hunt, look no further than the internet as many of developer CD Projekt Red's files were recently leaked.
An employee of the developer's Google Drive was accessed from outside sources over the weekend revealing the 64 square kilometer map, the story, mission information, and even the different endings.
Many times when information like this is "leaked" it can be taken with a grain of salt but these assets have been confirmed by CD Projekt Red in an email to GameInformer:
“It has come to our attention that, because of a breach of our security systems, some of the production files for The Witcher 3: Wild Hunt have emerged on the Internet. A portion of the files contains information about the story of the game so we strongly advise against accessing them, as this may heavily impact and spoil your future gaming experience. We'd also like to reassure everyone that the disclosure of said documents does not affect the development cycle in any way.”
If you're a fan of The Witcher series, it is highly advised to ignore looking at the assets but if you really find it necessary, the information can be found on Reddit along with every other leak in history.