I played it without playing any previous game and it was a blast, lore and history wise is self contained so no problem there.
I got the first Witcher game for free or near free with a GoG deal (after playing witcher 3), and it was very silly. I'll never be able to finish it, I don't think it aged well.
Witcher 3 is good and stands alone just fine. I suppose you could read the books if you get really into it and want more context.
You don't need to play any of the previous Witcher games in order to get the story, there is actually a little recap before you start the game.
Yes go for it. There is obv some history between characters, but the story is pretty self contained.
I'll offer a simple 'yes.' The game's story is easy to follow, but if you're unaware there are some NSFW scenes that may take you by surprise. It's combat is engaging, has good replayability through side quests and skill trees, and has great DLC. Hope you enjoy it!
Yes, no knowledge of previous games needed, like others already said.
Yes
Never played the other Witcher games, but TW3 is one of my all-time favorites and I completed the whole story (including DLCs) like three times already.
