Dodger:

Dodger By: Terry Pratchett
Fiction: historical, YA, 360 pages
Book Count: 12

This book does not take place in Discworld, but in Victorian London.  It also isn't a retelling of "Oliver Twist", so much as a story that if real might have influenced Dickens in his writings. (As he is one of the main characters in the story.) The book is about Dodger a young man that makes his living finding things in the sewers (or toshing), and also other odd and end jobs that may or may not be legal.  One rainy night he saves the life of a young women that is being attacked by a couple of men. Their lives become intertwined in an adventure that includes international intrigue, hobnobbing with the rich and famous, assassins, Sweeny Todd, cross dressing, the Peelers, Roman mythology, and espionage.