National Geographic Primary Readers is a high-interest series of beginning reading books that have been developed in consultation with education experts. The books pair magnificent National Geographic photographs with lively text by skilled children's book authors across four reading levels. This Set contains all 40 readers. There are 10 readers for each level: Level 1: Early reader These books contain simple sentences and are just right for kids who can decode with ease and are beginning to read fluently. They are ideal for readers of Yellow and Blue banded books. Level 2: Becoming fluent These books are a good match for kids who are developing reading stamina and enjoy a longer book. They are ideal for readers of Green, Orange and Turquoise books. Level 3: Becoming independent Best suited to kids who are ready for complex sentences and more challenging vocabulary, but still draw on occasional support from adults. They are ideal for readers of Purple and Gold books. Level 4: Independent reader Perfect for kids who are reading on their own with ease and are ready for more challenging vocabulary with varied sentence structures. They are ideal for readers of White and Lime books.