Books and Movies
You may not know this, but The Witcher 3 and all of the other games in the franchise are actually based on a series of books by Andrzej Sapkowski. These books tell the tales of Geralt of Rivia, a man who was mutated for the express purpose of hunting foul creatures throughout the land. They are very good reads, and the books will definitely provide an even stronger appreciation of the lore present in the meticulously crafted worlds of the video games. You can find all of the books on Amazon. There are five main books, but if you want to just get them started make sure to pick up “The Last Wish” which is the first in the series.
There are also movies set in the same universe and also starring Geralt of Rivia. You won’t find them by searching for The Witcher movies, though, since they are actually titled The Hexer. You may as well pick these up also to complete the trifecta of games, books, and film.