Without beating around the bush, the reading order for the Witcher books is as follows:

Confusion regarding the order is quite understandable. There is a handful of discrepancies which may make a new reader wonder. Let’s address them one by one to dispel any lingering doubts:

• Blood of Elves comes third even though in some editions it might say ‘Book 1’ on the cover. That numbering, if present, refers to the books in The Witcher Saga which consists of five novels. The saga starts soon after the events described in Sword of Destiny.
• Season of Storms comes last even though chronologically it takes place before the saga. It references events from the other books and was written with the assumption that reader is familiar with the rest of the series. Furthermore, the store of Blood continues straight after the Sword so it makes no sense to include a book in between.
• The Last Wish comes first even though it was published in Poland after Sword of Destiny. It’s a collection of stories which had been already printed in Fantastyka magazine. At that time, reader of Sword was aware of those preceding stories.
• Sword of Destiny comes second even though it was released in English fifth. This one is on the publisher who, I’m speculating, concluded that it was easier to market the saga.

Something Ends

Another noteworthy book is Something Ends, Something Begins (pl. Coś się kończy, coś się zaczyna). It’s an anthology including, among others, two stories related to the Witcher series: ‘A Road with No Return’ (pl. ‘Droga, z której się nie wraca’) and ‘Something Ends, Something Begins’.

‘A Road’ wasn’t planned as a part of the series but eventual later stories implied that Visenna described there is the same one Geralt meets in ‘Something More’. As a result, some consider the tale part of the canon. As far as I know, Sapkowski never categorically stated things one way or another.

‘Something Ends’ is a lighthearted non-canon story describing Geralt’s and Yennefer’s wedding. It was first published before the saga, yet it references characters and events from novels. Some call it an alternative ending though the author rejects such label.

As far as I’m aware, the two stories have not been officially translated into English.