Guards! Guards! by Terry Pratchett

In this book Terry Pratchett follows the logical consequences of professionalizing thieves in Ankh-Morph: the city watch becomes superfluous--except not, as an ambitious leader of a secret society uses a dragon to terrorize the city. This novel is rollickingly funny and a quick read to boot. The first few Discworld novels were difficult for me to appreciate, but I'm finding that as the series continues, the books keep getting better and better.