What is the main setting of The Lightening Thief? Based on the title, who IS the real lightening thief?

Percy Jackson is a demigod. He goes to camp half blood where he defeated the mintaur,from the stories..... then he finds out in his shield holds Zeus's powerful Lightening Bolt, where Zeus claims Percy has stolen. Percy insists he doesn't know what he is talking about and finds out that Luke Castellan, son of Hermes has stolen the bolt and hid it in Percy's shield.