Citizen of the Galaxy
Robert A. Heinlein
Now THIS should be made into a movie. Beggars and slums. Slaves, space going communities of traders, Galactic League troops. Pirates. It is like a Prince and the Pauper story, but... well I won't give it away, but it is classic Heinlein (1957). Hundreds of years in the future, BTW and people are still using slide rules! Very good story!