I've read some of the books/series mentioned here and I enjoyed them, but one author not mentioned is Louise Cooper.

I have read this series a few times since first discovering them at a SciFi bookshop in Sydney back in probably 1987.

    Time Master trilogy (1986):

    The Initiate
    The Outcast
    The Master

The bookshop assistant told me that if I bought the first book and not the second one I would regret it. The third book was not yet published, I think. It was good advice, especially since I lived 100 miles north of Sydney and would not go back to the big smoke very often and it was pre-online book ordering days. The books were "un-put-downable".

I also loved CJ Cherryh's Morgaine series, but I couldn't get into other books of hers. I didn't realise she wrote so many.

I loved Marion Zimmer Bradley's Mists of Avalon series, and also read as many of the Darkover series as I could get my hands on.

On the same theme, I loved Mary Stewart's Crystal Cave series and also T H White's Once & Future King series.

Pratchett of course. I read so many over the years that I reached my limit and overdosed. Good Omen was the first one I read and it is still a favourite because it opened my eyes to a new fictional world, the inner world of the workings of Pratchett's amazing mind. I can't wait to see the movie. I loved his Truckers series for kids too.

I read lots of Anne McCaffrey's Dragonworld series.

Ursula LeGuin has always been a favourite author of mine. I reread her books sometimes. I love the Earthsea series.

John Crowley's Engine Summer is different to anything else I have read, but doesn't count in this thread because it is not in a series.

Margaret Atwood's MaddAdam trilogy is dark and strange. But not as dark and strange and disturbing as the dreadful and interminable TV version of The Handmaid's Tale, which thankfully Ms Atwood is going to rectify by writing her own sequel.

I'm sure I can mention more. I used to devour Fantasy & SciFi until a couple of decades ago and then I just ran out of motivation to keep reading it.