•   Usually most of the books written by an author are the same level, some don't follow this rule.

    Black:
    "Wringer" by Jerry Spinelli
    "Thank You, Jackie Robinson" by Barbara Cohen
    "Ramona and Her Mother" by Beverly Cleary
     
    Orange:
     "Kidnapped" by Gordan Korman
    "Swindle" by Gordan Korman
               
    Purple:
     "Thirty Nine Clues"
                    "The Underland Chronicles" Suzanne Collins (some books are bronze)
    "Harry Potter" by JK Rowling (some books are bronze)
                  
    Bronze
     "The Hunger Games" by Suzanne Collins
    "Chronicles of Narnia" by C.S. Lewis