Monstrous Regiment — Terry Pratchett

War has come to Disc world . . . again.

And, to no one's great surprise, the conflict centers around the small, arrogantly fundamentalist duchy of Borogravia, which has long prided itself on its unrelenting aggressiveness. A year ago, Polly Perks's brother marched off to battle, and Polly's willing to resort to drastic measures to find him. So she cuts off her hair, dons masculine garb, and--aided by a well-placed pair of socks--sets out to join this man's army. Since a nation in such dire need of cannon fodder can't afford to be too picky, Polly is eagerly welcomed into the fighting fold--along with a vampire, a troll, an Igor, a religious fanatic, and two uncommonly close "friends." It would appear that Polly "Ozzer" Perks isn't the only grunt with a secret. But duty calls, the battlefield beckons. And now is the time for all good ... er ... "men" to come to the aid of their country.