Justyna There is a Kindle and paperback available now. It may only be a book of stories, but it is quite important transition from The Last Wish stories, to the books of the proper saga, explaining many crucial relationships between the characters.
☆Ruth☆ There is a kindle edition translation of Sword of Destiny that I know of as I have a copy. I haven't read it but it seems to be a collection of short stories and not a 'Witcher' novel. As far as I can make out the series of novels goes: Blood of Elves; Time of Contempt; Baptism of Fire; The Tower of the Swallow; The Lady of the Lake and a book called 'Storm Season' which I don't think belongs to the series. To make it even more confusing the second book Time of Contempt is listed as number 4 in Goodreads. Hope this helps :)