Night Watch: A Novel of Discworld (Discworld, 29) / Terry Pratchett,

Sir Sam Vimes gets knocked back in time thirty years in this rollicking adventure in Terry Pratchett's bestselling Discworld series

One moment Sir Sam Vimes is in his old-patrolman form, chasing a sweet-talking psychopath across the rooftops of Ankh-Morpork. The next, he's lying naked in the street, having been sent back thirty years, courtesy of a group of time-manipulating monks who won't leave well-enough alone. This Discworld is a dark place that Vimes remembers all too well three decades before his title, fortune, beloved wife, and child on the way. Worse still, the murderer he's pursuing has been transported back with him. And on top of that it's the eve of a fabled street rebellion that killed a few good (and not so good) men. Sam Vimes knows his duty, and by changing history he might just save some worthwhile necks though it could cost him his own personal future. Plus there's a chance to steer a novice watchman straight and teach him a valuable thing or three about policing an impressionable young copper named Sam Vimes.