Night Watch (Discworld)

Flung back in time by a mysterious accident, Sam Vimes has to start all over again. He must get a new name and a job, and there's only one job he's good at: cop in the Watch. He must track down a brutal murderer. He must find his younger self and teach him everything he knows. He must whip the cowardly, despised Night Watch into a crack fighting force - fast. Because Sam Vimes knows what's going to happen. He remembers it. He was there. It's part of history. And you can't change history . . . But Sam is going to. He has no choice. Otherwise, a bloody revolution will start, and good men will die. Sam saw their names on old headstones just this morning - but tonight they're young men who think they have a future. And rather than just let them die, Sam will do anything - turn traitor, burn buildings, take over a revolt, anything - to snatch them from the jaws of history.