The Mousehunter by Alex Milway

The Mousehunter is the story of Emiline, a mousekeeper for the richest man in Old Town. In Old Town, and the surrounding world, everything seems to revolve around mice. There are thousands of species of mice, some of which are common, some of which are only kept in the collections of the very rich. Many mice can be trained to use their natural abilities to help people - there are the highly trained Boffin Mice, who can manage mechanical controls; the dog-sized Elephant Mice who work as servers and carriers; the Powder Mouse, which can carefully carry gunpowder for use in cannons; and the Long-Eared Mouse, that turns into a frightening monster called a Grak when it is submerged in water. These mice, plus thousands more, populate the world that Emiline lives in, which is why mousekeepers are needed. Mousekeepers tend the mouse collections of others - in Emiline's case, it is the famous Isiah Lovelock's collection. But Emiline dreams of becoming a famous mousehunter, so she leaves Lovelock's employ to join the crew of The Flying Fox, run by Captain Drewshank. Captain Drewshank has just been given the task of capturing the infamous pirate Mousebeard. But as Emiline, and the rest of the crew of the Flying Fox, soon find out, not everything is as it seems in the cutthroat world of mousehunting.
This book was tremendously entertaining, and would be enjoyed by many older children, ages 10 and up. The world created by Milway is a unique one, being focused on mice as it is. Because of this it almost felt too shallow - there is no glimpse of what life is like for anyone not associated with mice. But maybe no such people exist in this world. It's hard to tell. The characters are rather shallow as well, although there is a good amount of question about who is good and who is evil, and what makes a person such. Overall this is a fun book, and is set up for a sequel, so undoubtedly we will learn more about this strange world as the story continues.