I read everything up to the Lady of the Lake, and it's good stuff. 

Well, we know Werewolves can have some degree of reasoning even in wolf form. A Witcher might hesitate to kill one if they think it can be saved or even more incredibly, if it hasn't killed anyone. Not all Witchers kill beasts on sight. Perhaps he isolates himself and feeds on animals. 

I know in one short story a werewolf comes by Geralt and Dandelion camping and doesn't attack because he recognizes Dandelion and listens to his music.