MacDonald is generally considered the first modern fantasy author. He was a friend of Lewis Carroll and encouraged him to publish Alice in Wonderland, a big influence on Tolkien, and C.S. Lewis called him 'my master'.

Lilith is a Christian allegory, and most people will tell you that you'll spend the first 50 pages asking, what the fuck is this? It's entirely possible you'll still be asking that if you stick to the end. MacDonald is generally revered by Christian universalists, of which I am one.