Dogsbody

A novel by Diana Wynne Jones. The guiding spirit of the star Sirius is framed of a crime and sentenced to reincarnation on Earth, in the form of a dog, unless he can come up with the murder weapon (which also happens to be a very powerful MacGuffin).

Tropes featured include:

 * A Boy and His X: Kathleen and Sirius--at least from her perspective.
 * Abusive Parents: Duffy.
 * Baleful Polymorph: Sirius as dog
 * Bittersweet Ending: See Death By Newbery Medal, below.
 * Cats Are Mean: Starts off this way, but they do mellow out part way through the story.
 * Cool Old Lady: Mrs. Smith
 * Death By Newbery Medal:.
 * Evil Matriarch: Duffy
 * Friend to All Living Things: Kathleen
 * Jerk With a Heart of Gold: Kathleen's cousins.
 * MacGuffin: The Zoi.
 * Orphans Ordeal: Kathleen's story, especially after.
 * Our Angels Are Different: Though they are called 'Luminaries' and rule planets, Sirius and his lot are winged celestial beings from a higher plane of existance.
 * The Troubles: Kathleen's father is an imprisoned member of the IRA.
 * The Wild Hunt: Sirius in his dog incarnation turns out to be related to them.