I can't speak for the witcher series as I've not read them or looked into them, but if wikipedia doesn't have anything I usually go to the fantastic fiction site for reading order Find it here they also are rather handy for chross series collections and if you just want information on say an author's alias.
I confess I am a bit of a stickler for putting my book series in chronological order, I even tend to number the folders, eg, I have a Harry potter series folder and then 01 Harry Potter and the philosopher's stone, 02 Harry potter and the chamber of secrets, right up to 08 Harry potter and the cursed child .
I'm afraid I don't have a lot of patience with goodreads, since other than the publisher's summaries, the site seems very clutter and the majority of reviews I've seen on there are either one sentence "you should read this book because it is a good book" or "I like this book because I am a feminist pagan lesbian magician and the book expresses my feminist pagan lesbian magician values" eg, reviews that talk more about the reviewer and how hip and trendy their own ideas are than about the book in question.
Btw, I approve of feminists, pagans, lesbians and magicians for that matter, but the reviewer I mention really was a pratt.
I suspect there are some reviews and intelligent people on goodreads, but I find wading through the drek a bit of a chore, one reason I to confign my review searching to either fantasybookreview.co.uk where hopefully the official site reviewers know what they are talking about (well accept for that lunatic called Dark of course), or a few people on tor.com such as Leigh butler or mari-ness who's opinions I find interesting to read.
With our dreaming and singing, Ceaseless and sorrowless we! The glory about us clinging Of the glorious futures we see,
Our souls with high music ringing; O men! It must ever be
That we dwell in our dreaming and singing, A little apart from ye. (Arthur O'Shaughnessy 1873.)