The Lightning Thief by Rick Riordan

Percy Jackson has never really fit in. It wasn't that he ever tried to bring about disaster or anything. However, disaster can't help but follow him around. After Percy is kicked out of yet another school his mother takes him to the beach just to get away from it all. That is when things really start to get weird and Percy finds out that he isn't completely human at all. He is a demi-god, a half mortal child of one of the greek gods. Percy is sent on his first (and maybe his last) quest to get back Zeus' lightning bolt before a war breaks out between the gods. Oh ya... he only has two weeks to find it.