When Harriet grows up a little and discovers that she's cursed to be pricked by a hamster wheel on her 12th birthday, she is overjoyed. If magic foreordains her pricking on her 12th birthday, that means she's invincible: the magic won't let anything kill her until then. So she takes her leave of her parents and sets out to kill or at least beat the tar out of every single monster in the world by the time she turns 12th. When her parents tell her this isn't princessly behavior, she retorts that she's a princess, so by definition, whatever she does is princessly.
That's the setup, and it goes to some very funny places, as Harriet returns home just before her 12th to pick the prince she'll be promised to; he'll stand by to kiss her ten seconds after she is pricked by the wheel (Harriet's parent's aren't stupid, after all), and then there's a twist that ends up with Harriet being the only one who isn't cursed and now she has to go find a prince to kiss everyone in the castle to wake them up.
Together with fantastic comedic illustrations and hilarious dialogue, this is about as charming as can be — and there's several more that follow!
Many thanks to Michelle Sagara West at Toronto's BakkaPhoenix Books for recommending this one.
Hamster Princess: Harriet the Invincible [Ursula Vernon/Dial Books]
