Audiobook Title:
Monstrous Regiment
By: Terry Pratchett

But there's a war on. There's always a war on. And Polly and her fellow recruits are suddenly in the thick of it, without any training, and the enemy is hunting them. All they have on their side is the most artful sergeant in the army and a vampire with a lust for coffee. Well...they also have the Secret. And as they take the war to the heart of the enemy, they have to use all the resources of the Monstrous Regiment.