This is a very difficult book to classify: historic-tick; fantasy-tick; war-tick; horror-tick; romance-(small) tick!
I found myself finishing this at 4 in the morning - I needed to know how Wynne-Jones was going to tie all the strands together, and he does it with panache! You do need to suspend disbelief, and if you don’t like a touch of the supernatural in your reading, then you will probably not be satisfied with this book.
Ultimately, this is a study of how the characters deal (or not) with grief. But it’s not a morbid read at all and I would highly recommend it to readers from Years 7+. I feel boys in particular would relish the ghoulish aspects in the book, but there is also a reasonably subtle message about the futility of war.