The Ankh-Morpork City Watch series is easily my favorite of the Discworld novels, because of my particular interest in Public Administration. The AMCW series asks all the right questions about law, jurisdiction, enforcement, and vox populi, without resorting to cheap preachy answers.

But this book stands out as the best of the series so far, taking all those questions and mixing them in with the science fiction device of time travel, and delving into not just Public Administration questions, but also sociology and deep psychology.