The Witcher games are based on the books by Andrzej Sapkowski, they have a bit of a cult following in Poland. I think the first book has been translated into English.
You don't need to have played the 1st game to understand the 2nd, as they are separate stories, although it would help to have played the 1st game or read the books to understand some of the lore.
For example Witcher's are pretty much seen as freaks, in the 1st game most people in towns react aggressive to you. Witcher's are mostly employed as bounty hunters, killing monsters that plague towns and city's, except Dragons! A Witcher does not recognise a Dragon as a monster.
Oh and a Witcher is not capable of getting a woman pregnant and they have some magic abilities and can use potions which are actually mutagens. They would kill normal humans. Last but not least the Witcher carries two swords, steel for killing humans and silver for killing monsters.
The game plays really smooth with a pad. which was a big surprise as I mostly believe mouse + keyboard > everything else.