Monstrous Regiment (Discworld 31)

Polly Perks joins the Discworld army to find her brother Paul. "Ozzer" cuts off her blonde braids, dons male garb, belches, scratches, and masters macho habits - aided by well-placed pair of socks. The legendary and seemingly ageless Sergeant Jackrum accepts her plus a vampire, troll, zombie, religious fanatic, and two close "friends". The best man for the job may be a woman.