The first time I read Susan Cooper's The Dark is Rising series, I did it all out of order. The first of the five books I read was The Grey King (which is the fourth book), followed by the last book in the series, Silver on the Tree. Then The Dark is Rising, (and I was young when I read them, young enough that I spent my entire eleventh birthday wishing with my whole self that I would learn I was an Old One), then the two books that star the Drew children, Over Sea, Under Stone and Greenwitch.
These are books that made me. The Grey King was the first Arthurian story I ever read, and made me want - so desperately I wrote him into my own first novel - a dog named Cabal (Cafall, in the Welsh.) They made me begin to think about different ways of telling a familiar story, were the start of my obsession with finding more and more obscure variants of the story of the Matter of Britain. I wanted to be Bran Pendragon, and even though now, as I reread them, I understand why the story required he choose as he did, I know that I would have made a different choice at the end. I have attempted to learn Welsh because of these books. They are amazing.
The most amazing part, for me, is how well they hold up. I am shocked, now, as I reread them, at how short they all are - the longest probably only 65K words, Greenwitch half that. There is just so much in each of these books. Cooper never assumes that her audience of children is stupid or incurious, or will be thrown out of the story by strange names and funny language.
And yes - they are plot coupon fantasies. The goal of each book is to find the magic thing, or things, first, and get them to the right place or use them properly. But the simplicity of the plot structure doesn't mean these are simple books.
In her book, The English Romance in Time (highly recommended for anyone interested in thinking about the roots of modern fantasy), Helen Cooper notes that one of the things that made the medieval romance an unique genre was its interest in stories about women with agency. (NB: This does not necessarily mean that we, as modern readers, would call these feminist stories. What it does mean is, for the culture and the time - England, beginning about 800 years ago - these were stories about women exercising power.) Cooper uses Greenwitch, the middle book in the series, to tell a woman's story, to explore female power and magic in the middle of a quest narrative.
Cooper also makes clear that the Light can be as harsh a master, and as unconcerned about normal human consequences as the Dark. The Light wins, but the victory is not without cost, and loss. This strikes me as a brave choice for a writer to make, but also the right one - if the object of the quest is worth winning, perhaps the winning should not leave those on the quest unscathed. She shows that being the Chosen One can be as lonely as it is special, and that great responsibility is sometimes a burden.
And it is The Tempest that makes the mountains sing. Is it any wonder I love these books?