Thud! is Terry Pratchett's 34th Discworld novel, released in the United States of America on September 13 2005, the United Kingdom on October 1 2005, and may have been released before that date in other countries, such as Norway and Denmark.
As the book opens, a dwarven demagogue, Grag Hamcrusher, is apparently murdered. As ethnic tensions between Ankh-Morpork's troll and dwarf communities mount in the buildup to the anniversary of the Battle of Koom Valley, Lord Vetinari convinces Commander Vimes to interview a vampire applicant to the Watch. The new recruit, 51-year-old Salacia "Sally" von Humpeding, becomes, along with Angua and Carrot, attached to the investigation surrounding Hamcrusher's death.
Meanwhile, Nobbs and Colon begin an investigation into the theft of the fifty-foot painting The Battle of Koom Valley by the supposedly-insane artist Methodia Rascal from a city museum. Nobbs has a new girlfriend, the exotic dancer Tawneee (pronounced with each "e" as a separate syllable); Nobby first caught her eye when slipping an IOU into her garter.
A recurring element in the book is Sam Vimes' race to get home every night by six o'clock to read the book Where's My Cow? to his infant son, no matter what; Pratchett uses this theme as a symbol of Vimes' determination never to compromise his own morality. Another is the game Thud, which first appeared in Going Postal; the game, which is a symbolic replication of the Battle of Koom Valley, requires the player to learn to think as both sides.
We learn more about the werewolf/vampire tensions, as Angua resists the urge to fight Sally over every tiny detail.
Many of the book's elements, particularly mistrust of outsiders, latent racism, and the bringing home of faraway ethnic conflicts, coincide with then-current events in Britain — although the book was completed before the 7 July 2005 London bombings. The character of Grag Bashfulsson echoes a contemporary debate in British Islam about the lack of home-grown imams to preach in local mosques. The Dwarfs and Trolls of the Discworld have often been used as allusions to warring ethnic and political factions, especially how Westerners can come to terms with and understand them in a more positive and rational light.
The subplot concerning alleged "hidden messages" in the painting of Koom Valley, and the accompanying conspiracy theory book, The Koom Valley Codex parodies The Da Vinci Code by Dan Brown.