Just beat the game. I'll try to minimize spoilers.
Quite frankly, I think it's a novel worthy story. That is to say it's that good. Of course, that's also ignoring the poor english localization. The overall story is just good. To compare it to Mask of the Betrayer, I'd say MotB had more interesting characters, Witcher had a better story.
I thought it did very well what it set out to do, as well. Blur the lines between good and evil. Sometimes it did fall short, at one point a character tries blaming Geralt for all the bad things that have happened so far, which is a point easily defensible against. At least in my game. However, the ultimate villain of the game was a sympathetic character to me. His position isn't entirely new, as I'm sure I've seen it before, but the way they presented it along with my realization of who he is had me feel sorry for him in some ways.
Another flaw in the game is that it's uneven in a way. Chapter 2 and 3 feel like just one long chapter. When I hit 3, it felt repetitive. But once I was done with that, smooth sailing.