In the book Percy Jackson : the Lighting Thief, by Rick Riordan it has a whole combination of action, romance, and thriller. Percy the main character is a demigod, half human half god. He is son of one of the three brothers Poseidon, the god of the seas. In the book Percy and his two friends Annabeth Chase, also a demigod daughter of Athena, goddess of war and wisdom and his bestfriend Grover Underwood a satyr travel in a journey to the Underworld to save Percy's mother from the god of the Underworld Hades. Throughout the book their are many symbols that are really important.
     Symbols are the important objects or things that are important to the main idea or the whole story of the book. First, there is Percy's pen which turn in to a sword. The pen/sword is important because without the pen Percy will never have been alive because that is his only weapon and also the only thing his father, Poseidon left for him. The second one is the lighting bolt, weapon of the god of the sky's and all gods and goddesses Zeus. Without that lighting bolt missing there would have been no story and no story line. The third most important one is the shield that one of the counselors from camp Half Blood gave him on the journey to be safe. The shield plays an important role because the shield was the object that had a secret compartment that held the lighting bolt that the counselor tried to frame Percy for. Obviously he didn't get away with it because Percy found out. And the fourth and last important symbol in this book is Percy's mother, Sally Jackson who was attacked by one of Hades monsters that he sent to pretend that Sally was actually dead to Percy, but Percy didn't buy it. Sally is an important symbol because if she didn't get captured by Hades then Percy wouldn't have gone to the Underworld.
     Throughout the book there are many symbols but I think that these four are the most important in this book. I am very sorry if I have spoiled some parts of the book for you.