the fourth and last book in the Enchanted Forest Chronicles, if you start with Talking To Dragons, which I recommend.
Told from Morwen's point of view, starting with a rabbit that grew six feet tall. After she starts investigating its reports of the magic that does it, it eats one of her cabbages, which turns it into a donkey. Setting out with the news of the wizard behind the first spell, to see what can be done, she finds at the castle that, at first, Mendanbar is over-zealous about Cimorene, because she is pregnant. The revelation of what the wizards are up to, however, gets things moving. It means the wizards have found a way about the protective spell. And then they realize the magical sword that protects against them has been stolen.
So, the quest must set out. In the course, there appear a pantry that can produce clover, the rabbit's foolishly eating more things that interact with the magic, vines that appear only by night, a tower with a fire-witch in it, a cat sitting on the chest of an injured man, a trudge through swamps, old MacDonald's farm being redone, and magical mirrors, among other things.
I'm afraid it suffers a little from being a prequel, since this is the volume in which Talking is set up.
Light and frothy and fun. Though it was reading this that I realized why the prequels were not so good as the first book: the characters know too much. Not just in the sense that they are older than Daystar was, but that they are familiar with the conventions and tropes of the stories they expect. Talking had more doubts and uncertainties about events that could come to pass. Which means the prequels have more limits on how much drama they can have.