Night Watch by Terry Pratchett, 2002

Night Watch by Terry Pratchett. ISBN 978-0-857-52504-8.

Guard Captain Sam Vimes suffers a mishap. He wakes up a bursting neck in his own past, in a darker and more dangerous Ankh-Morpork where a sadistic secret police bores beggar cubs and the poor to death. There he must take the role of Keel, the straight-backed citizen who undertook to raise the young Sam Vimes, and who died a tragic death during the rebellion Sam knows will soon break out! To further complicate life, a psychopath from the future is pursuing a career in Cable Street Unmentions. Sam gets his ears hot if he's going to manage to raise himself, prevent a disaster and also get back to a bearable future. A Discworld adventure with a Dickensian atmosphere among street children, licentious women, rebels and secret police.