I haven't read the books but have played the game, and still like it. I am having a hard time adjusting to their casting choices for Yennefer and Triss (ESPECIALLY Triss), both for looks and personality (the game really sets up Yennefer as a stone cold bitch, and the current Yen just isn't hitting the mark). I had my doubts about Cavill as Geralt, but I think he's great in that role and really nailed the personality/nuances. I think the actor cast as Jaskier was spot on, too.
The biggest complaint I keep hearing from people is that the timeline is confusing, but I thought after a few episodes it was pretty clear that we were talking about multiple converging timelines, one short vs. one decades long.
I suspect the following seasons will really pick up the pace and Netflix will take the season 1 feedback to improve upon it, so I'm really looking forward to it.