Pratchett's a polarizing force in literature. Many people dislike his writing because they dislike the fantasy world in which he sets his Discworld novels. I have a very low dragon/leather/quest/wizard threshold and yet I love his books--why? I can only assume it's because I love his humour. It's about life and what's good, bad, and silly about it. He takes sharp pokes at religion, science, politics and love, all by turning the tropes of fantasy fiction back on themselves.
His characters are very rooted in rural English life, so the people in his books are what everyday English folks would be if they were thrust into this bizarre world fuelled by magic. All Pratchett fans have their favourite character: is it Rincewind, the hapless would-be magician; of the Witches who overcome obstacles more through understanding how people work than through magic; or is it (like me) Captain Vimes, the archetypical world-weary good cop? All the Vimes novels are thrillers/mysteries, and this is no exception.
I've followed Vimes through several books now, and each just gets better than the last. He keeps getting promoted, which takes him further from the streets and the hands-on policing he likes. This book sees him thrust back in time to mentor a younger Vimes during an upheaval in the city's rulers. There are a lot of very pointed observations on the difference between a police force, secret police, and an army, and Vimes's wisdom, clarity of thought, and determination to do the right thing in a complicated world is a pleasure to behold. If you read between the lines (or sometimes even on the lines) you'll find some very relevant observations on the War on Terror.
This is as good an introduction to Pratchett's Discworld universe as
any, although it features very few of his other staple characters.
Newbies to the Discworld might want to read this with an eye to then
reading all the novels in sequential order. If you are already a
Discworld fan, then all you need to know is that this book is out and
you should order it immediately
[*] Might be biased in that I think Pratchett's one of the top three authors writing today. Period.