Even some of the biggest games around these days had to start somewhere. Geralt of Rivia from The Witcher franchise began life in the pages of the short stories and novels of Polish author Andrzej Sapkowski.
First printed in 1986, The Witcher originally appeared in the Polish sci-fi and fantasy magazine Fantastyka. The first short story was the author's entry into a writing competition the magazine was running -- and it came in third place. Since then, more short stories featuring the adventures of Geralt were published and eventually collected into one volume in 1993.
Polish developers CD Projekt RED released the first game in the series on PC in 2007 -- the beginning of which followed the first book, The Last Wish. But that is where the similarities in storyline end. Of course, the main premise of the books is still in the games, but each of the games develops its own story to expand upon Sapkowski's original vision.
The books are still available on Amazon, and it would be a good idea to start with The Last Wish -- as the short stories in this volume will introduce you to the written word of Geralt. There is a whole host of The Witcher games on Steam as well, including plenty of expansions and DLCs.