The metaphors are striking, the prose graceful, the plot fairly interesting - but I lost interest in the teenagers' coming of age problems after a few chapters. So I stopped reading, but wonder if Stiefvater has any fiction with older characters?
She doesn't, unfortunately. But I would urge you to give the book a second chance. I think the themes of platonic love carry this book way far past the "coming-of-age" problem, and into universal themes that carry on into adult novels.