Princess Mirella has run away from her family, from her castle, from being a stuffy princess who has to be polite and marry any old Prince who will have her. And she's run to Oglefort, where there's an ogre who, she hears, will change anyone into an animal of their choosing.
Alas, the ogre has recently lost his wife, and is determined not to change anymore people into animals--it's not very ogreish to make people happy, after all. Instead, the ogre has decided to die. So he enlists the help of Mirella--and the hag, and her familiar (an orphan boy) Ivo, and the troll, all who've come to kill the ogre and save Mirella--to plan his funeral.
And there are ghosts and armies, and ogre aunts and happily ever afters, and this, which is the last line of the book:
"Anyone who has an egg to watch over has a stake in the future, and the future--they were sure of it--was going to be good."
Which is really an amazing note to end a career on. Right on Ms. Ibbotson. You are missed.
I will say, I didn't enjoy this book overmuch. It was dark in the right ways, gross in the wrong ones (and that's for me, I am just a person who does not enjoy gross), and funny in ways that are alien to me. I liked it, but I couldn't love it, because I am not the reader this book was looking for. Seriously, I think this was a great book, but it was not my book.