The show is based mostly on the first two books of short stories. If it continues it could rival GOT in length. There are several seasons worth of content to get through. Henry Cavill does an excellent job as Geralt although it's unnerving to see him look so much like the video game character. Some people have criticized Cavill's performance as flat but may not have read the books. The Trial of the Grasses took a lot out of Geralt. He doesn't have normal human affect. His response to social situations is very much in keeping with book Geralt. Joey Batey as Dandelion (Jaskier) is excellent. Dandelion is as egocentric and childish as Batey plays him.
The show is not faithful to the plot in the short stories in detail. There is some telescoping, addition, and conflation. The overall picture is better. The first season deals with the development of Geralt's involvement with Ciri and Yennefer and the war with Nilfgard. The tone is spot on. This is not your typical sword and sorcery story. People's motives are complex and often not as they seem. The triumph of good over evil is not a feature. Sometimes, like the books, the moral side seems a bit didactic but it's mitigated by some interesting characters and monsters. There's a reason that the lighting tends to be dim.