Guards! Guards!

Guards! Guards!  - Terry Pratchett Introducing the Ankh-Morpork City Watch.
Captain Vimes, Sergeant Colon and Corporal Nobby are considered a joke by the other inhabitants, not really expected to do much (which they do quite well).
Into this little circle comes Carrot, with his ideas of what law & order should be in a big city.
Raised by Dwarves, it's all a bit vague to him, but he has a sense of right and wrong and the build to back him up.

As the city is ravaged by a dragon, which shouldn't exist, the Watch find a purpose and their own sense of destiny.

Not really a laugh out loud book, but Pratchett has a good eye for what makes people tick and some nicely absurd moments.