This is the first book of a famous Polish series of fantasy novels on which the Witcher video game was based. I started the book (in English translation) while playing the first game and I certainly recommend the book as an adjunct to the gaming experience. It gives a new appreciation of how well the game sticks to its source material.
The book is really a collection of short stories held together by a common thread of a witcher recalling past adventures as he convolesces after a nasty wound. The gritty character of the Witcher and the World he lives in is quite compelling. Witchers are highly trained killers with enhanced fighting abilities who hire themselves out to kill monsters. The hero Geralt is basically good but also cynical. He had learned not to get involved in other peoples problems. The closest parallel I can think of is Clint Eastwood in the famous man with no name Westerns.
The stories themselves are interesting enough but the writing style in translation is quite flat and becomes tedious. I don't know if this is the fault of the translation our whether it reflects Sapkowski's underlying writing.