I sometimes think there are two Terry Pratchetts. One is the always joking, laugh-a-minute Pratchett and the other is the more serious and thoughtful Pratchett. Both sides are welcome and entertainin and Monstrous Regiment is definitely from the pen of the later. It's the story of Polly Perks who, disguised as Oliver Perks, joins the Borogravian army at the tail end of a hopeless war. What unfolds is a story that investigates the absurdity of war, sexism, fundamentalist religion and nationalism all the while extolling the virtues of heroism, camaraderie and the importance of an extra pair of socks. I truly believe that it is one of Pratchett's finest additions to the DiscwWorld serious.
I've read just about every book Terry Pratchett has written. In my opinion this is quite possibly his finest work.
Not my favorite of the Discworld novels, but still highly enjoyable. Polly Perks joins the Borogravia army to find her brother and bring him home. Since it is an Abomination unto Nuggan for women to be in the army or wear men's clothes, she pretends to be a man to join. Along with her little troop of "brothers", Perks learns what it really means to be a soldier and proves her worth to her commanders and country,