The Battle of the Labyrinth by Rick Riordan is the fourth installment in the Percy Jackson and the Olympians book series. This time, Annabeth Chase receives her first quest. Instead of 3 people coming on the quest, Annabeth chooses 4 of her friends, breaking the rules. They venture into the labyrinth and encounter new monsters (or are they technically ancient monsters), old enemies, the goddess Hera and even a milkman. All this ending with an epic battle. Become the fifth member of their quest and read The Battle of the Labyrinth. I recommend this book to grades 3-5.