The guys at Fantasy Fan let us know that they've published an article that attempts to "clear up any misconceptions" people might have regarding Andrzej Sapkowski's Witcher novels after playing CD Projekt's The Witcher.
The first misconception I've noticed is caused by the fact that the game has reached a greater audience than the initial translation of the Witcher books. I can't stress enough how important it is to remember that the game was created based on the brilliant writing of Andrzej Sapkowski. The books are not mere extensions of the successful game drawing from its success. Remember, the books were first!
The second issue I noticed was born out of the attitude triggered by the movie industry. "I've seen the movie (or in this case, played the game), I don't need to read the book. It's going to be the same story only it'll take longer to get through." Nothing is more wrong, my friend! The game is not based on The Witcher books. It's actually happening after the events described in the Witcher saga. You are taking over the character of witcher Geralt, but the story is not directly connected to the books. Andrzej Sapkowski, who wrote the books did consult game makers in their creation, so even though you'll be entering a new adventure, you can rest assured it's going to be as entertaining and morally complex as the books.