Oh this is one of those books that are so difficult to review. All books don't suit everyone, like music, or food, and this is one that I think you must either love or hate. It's like reading a Grimm's fairy tale, as narrated by the little prince, it's the reading equivalent of Elsa Beskow's paintings or those wonderful (fake, I know, but still wonderful) Cottingley fairy photos.
I think the only book that I've ever read that had the same sensibility was Winter's Tale by Mark Helprin. Or perhaps some of Neil Gaiman's short pieces (I am a fan of Gaiman's novels, but it's in his short stories he reaches this sense of both gravity and whimsy at the same time. I wonder what he thinks of this book?)
It's big and sprawling, covering decades and generations, and yet it's always intimate. The language is gorgeous. The story is at once mystical and completely easy to follow, there is foreshadowing aplenty if you care to see it, and the whole thing is simply delightful.
To anyone who ever imagined their were fairies at the bottom of their garden, I cannot recommend this book highly enough.