In the 1960s and 1970s, I read quite a few of Mary Stewart’s books. At the time, she, along with Paul Gallico, was one of my favourite non-genre authors. She was very popular indeed and managed to break out of genre labelling with her suspense, mystery and fantasy works.
She wrote about contemporary and historical periods with equal assurance, whether the settings were Crete, Corfu, Austria, Lebanon, Provence, Northumberland, Cornwall, or the Scottish Hebrides.
It’s a long while back since I read her books, but I recall that my particular favourites were:
Touch Not the Cat (1976) about a heroine who possesses the gift of telepathy and involves suspense, deceit and attempted murder.
Madam, will you talk? (1854), her first published novel is a murder mystery set mainly in France.
And of course the Arthurian trilogy The Crystal Cave (1970), The Hollow Hills (1973), The Last Enchantment (1979). (I have still to read the succeeding books in the series, The Wicked Day (1983) and The Prince and the Pilgrim (1995); yes, I know, I have too many books still unread!) These books inspired the acclaimed BBC TV series Merlin. [In my as yet unpublished time-travel dystopian novel Time With A Gift Of Tears, my hero travels to Arthurian times and arrives in a crystal cave; my nod to her book).
You can get view the original blurbs and dust-jackets of her novels here
An excellent writer, who put you there, in the scene, and made you care about the characters.