Mastiff is the final book in Tamora Pierce's Tortall prequels about Beka Cooper, cop and direct ancestor of George Cooper, best known for his relationship with Alanna. Beka writes her own books, recording her story mainly as part of the official record keeper she does for her job, but also using the books as a journal since I think she plans on copying them out of the code used by her department before turning them in. Or maybe she just doesn't have much sense of privacy, I forget.
Anyway, Beka writes about feeling fraudulent at her fiance's funeral, because she had been planning on leaving him anyway, partly because of stupid behaviors that did indeed lead to his death. It's almost a relief when an emergency call drags her out of the city for the most important case of her career -- rescuing the young crown prince from his kidnappers.
Beka wrestles with the ideas of friendship, relying on her dog and her partner and his lover while learning to trust and then love the goofy mage also assigned to her party. The question of trust plays a large role -- the absolute trust between a dog and a handler, the trust between lovers, between partners, between servants and masters, between royalty and subjects. What happens when trust is betrayed? What about when it is abused? There are major betrayals at many levels, as well as small ones. Obviously the rebellious nobles who orchestrated the kidnapping personify betrayal, but what about a fiance who never trusts you to do your job? Or never listens when you ask for or refuse help?
Pierce also uses this book to attack slavery, which is a common practice in her world. Beka confronts the dangers and horrors of this practice in steadily building scenes as she gets closer to the prince, who is learning about the pains in a very personal way. The final solution seems very idealistic, but that is a Tortallan tradition. Beka's viewpoint keeps the book focused but limited; this is a good book for Pierce enthusiasts but probably a poor gateway into her worlds.