I'm a bit new to this site this might be terrible.
I read this 4 years ago. There were three main characters - two girls and one boy. They were on a planet. I think maybe the main inhabitants were French. There were three classes. One of the girls is a pickpocket, the other girl is a guardian of a library and the boy is a government official in training. The people don't know how to read. They have screens in their arms that they get broadcasts from. It was a pretty big book with a lot of pages and one in a series. The main antagonist was the boy's grandfather who lead the police/military force.
I read this 4 years ago. It was a pretty big book with a lot of pages and one in a series. Does any story fit this description?