I wish there was an in-between option for reviews. I'd say if you love The Witcher and want to see more of his story, get the game. If what you are looking for is a good gaming experience, go elsewhere.
I loved the first Witcher game, but I cannot say the same about The Witcher II. The only reason I continued playing is to see more of Geralt, despite any annoyances. When I started the game, the graphics were busted - the sky an intense white with blue edges. After consulting with Uncle Google, I found I had to go into the files and delete brightness to fix it (apparently a relatively common issue?! why?!?!). Even with that fixed, I found the visuals just a little too vibrant and saturated for my liking - I did get used to it eventually, though.
BAD MECHANICS
The default key bindings are awful and you can't change them easily in game, you have to go to the launcher and find it in well hidden settings. Why?! Still, some keys (inventory I or map M) cannot be rebound - and I consider those keys pretty inconvenient.
This game just has a lot of small annoyances. I sometimes found it a little tricky to collect loot, to stop at the right place to click on it. The maps are horrible. From an artistic view, they are very pretty, but they are so impractical, hard to actually use to get anywhere. The minimap on your screen rotates based on the direction you are looking in, it does not point north, which makes orientation harder for me (at least it does have a small arrow pointing north, but still).
Once during a game of dice, I lost despite having a two and my opponent having nothing?! I'm also unsure why they chose to change the design of the dice to be hard to read and you now also have to manually roll the dice at a weird angle - you can also lose the dice if you roll them wrong???
The combat in this game is a lot more complicated than it was in The Witcher I (and I really liked the simplicity of combat there). Now you have to press keys to parry or dodge at the right time, you can throw daggers and bombs, but I find it extremely hard to aim them. And of course you can still use five signs and give either fast or strong blows with your two swords. That's all way too much for me (and honestly most of the other mechanics take too much time to employ due to long animations, so merely swinging a sword ended up usually being most efficient), but thankfully there are many combat difficulties to choose from. So while I miss the combat from The Witcher I, I suppose this way might suit a wider range of players?
THE STORY
The story of the prologue is non-linear, jumping back and forth. Not something I appreciate much, honestly I didn't much like the prologue as a whole - which isn't good, you would really want the first couple hours of gameplay to hype you up for playing more. Here, the prologue is something to be suffered through to get to the good part.
Thankfully the rest is mostly linear, three chapters that each take you into a different region with new quests and monsters to defeat (though the third one is really really short). This is the part of the game I enjoyed most.
There is a major plot divergence going from first to second chapter, your decision completely changes your following experience - which means if you want to see it all (and to get all achievements), you definitely have to replay. Personally, I'm content with my chosen path and don't find it tempting at all to return to this game for a re-do. Be prepared for lots and LOTS of politics talk. It took me about 30 hours to finish the thing at a slow pace, unlike the 50 hours the first game had taken. I assume this is the consequence of having big divergence possibilities.
In chapter II, there were some random references to the Lord of the Rings and I'm not entirely certain what to think of them. I love LOTR, but here it felt like a weird jump away from the witcher universe. It would be different if the whole game had a light, humorous feel, with references to different works of fiction thrown all around, but here, I don't think it quite belonged.
Another little thing I found annoying sometimes - they would let you fight someone, you gloriously kick their behind into next Sunday, but then suddenly there's a cutscene with you being the one who got crushed like an ant. Come on! Either don't let me fight them, or make them undefeatable!
Very last thing to complain about - the very end I just came from! They tell you that to see the final epilogue you need to watch the credits. Don't. The credits are SO LONG, even if you hold LMB to speed it up, only for the game to show you the Nilfgaardian army invading. So stupid and not worth the time - I don't know what they were thinking, it's not like anyone will actually read the credits even if we are forced to wait for them to go by. It's just one final annoyance to make you upset as you write your review.
MODS
There are many mods available on Nexus Mods, which can improve graphics, adjust carry weight etc. There are ways to personalize some details you may not like, so at least that's a big plus for the game. I would suggest you use them to make the best of this.