The Witcher is one of my favourite RPGs of this generation. I've played it on both PC and streaming via Onlive. It's definitely more playable on the PC! The combat is pretty simplistic - you choose the right kind of weapon, and then the right "style" (e.g. fast/slow/group) for the enemy you're attacking. There's also an alchemy system that gives you buffs to help make certain tasks easier - so you get healing, the ability to see in the dark, etc.
It's not the combat that makes this fun, though, it's the story. I've read most of the books that have been translated into English, and I think they did a good job tying the game into the world of the books. The story is quite long, and you really get to know the characters and immerse yourself into the universe.
I prefer The Witcher 1 to The Witcher 2 (the graphics might be better in 2 but the story went in the wrong direction IMO and there wasn't enough of the monster hunting side of being a Witcher for my tastes). I'm looking forward to The Witcher 3 though.