Monstrous Regiment, A Discworld novel

Despite her rapid mastery of belching, scratching, and other macho habits (and aided by a well-placed pair of socks), Polly is afraid that someone will immediately see through her disguise; a fear that proves groundless when the recruiting officer, the legendary and seemingly ageless Sergeant Jackrum, accepts her without question. Or perhaps the sergeant is simply too desperate for fresh cannon fodder to discriminate - which would explain why a vampire, a troll, a zombie, a religious fanatic, and two uncommonly close "friends" are also eagerly welcomed into the fighting fold. But marching off with little (read: no) training, Polly (now called "Oliver") finds herself wondering about the myriad peculiarities of her new brothers-in-arms. It would appear that Polly "Ozzer" Perks is not the only grunt with a secret. There is no time to dwell on such matters, however. Duty calls. The battlefield beckons. There's a tide to be turned.