Sally Gardner's first novel is a hodgepodge of elements, each interesting in its own right, that never really come together to form a coherent whole. One part is a historical novel about a girl growing up when the Puritans took over England. The second part is a fairy story, with a wicked queen in Fairyland, a prince bespelled into animal form, romance, revenge, and magic. It is the intersection of the two that just doesn't work.
The author must have had trouble with it too, as she suddenly wraps up the whole thing on the last two pages, with no explanation or reason for things working out the way they do, as if she had suddenly run out of ideas, couldn't get it to work, threw up her hands, and ended with "and then they all lived happily ever after." Though erratically paced and emotionally distant, there's a lot of vivid writing here, and perhaps with more experience Gardner will be able to construct a plot that makes more sense.