The Lost Hero by Rick Riordan

The Great Olympus, where Greek god abodes after dethroning the mighty, bestial Kronos, are in a state of turmoil. Gaea, the goddess of Earth is about to be awaken from her dormant state thus unleashing the wrath on Olympus.But there is a lost hero among 7 demigods which as per prophecy will save the Olympus from the claws of uprising giants. 
An amazing work of fiction, with Greek mythology characters making it one of adventerous trip hard to miss.