Good news if you can read Polish: Andrezej Sapkowski is releasing a new Witcher novel, Storm Season, on November 6th. The new book will be a prequel to the five-novel series. Unfortunately, no word on when it will be translated to English.
In Sapkowski's books, witchers are monster-hunters who receive special training and have their bodies modified at an early age to provide them with supernatural abilities so they can cope with dangerous monsters. The books have been adapted into a movie and television series, a video game series, and a graphic novel series. The novels (excluding the short stories) are also called the Witcher Saga. So far, the books The Last Wish, Blood of Elves and Times of Contempt have been officially translated into English.