The 21st Century Basic Skills Library helps young readers develop fluency as they learn about the world around them.Level One books are for readers with beginning reading skills. They contain 75-100 words. Simple, short sentences using many short vowel words comprise the text. Words and illustrations are familiar to young readers. Four to six content words are included.Level Two books are for readers with intermediate reading skills. They contain 100-150 words. Words become more challenging, but there are very few complicated word patterns. Most words and illustrations are familiar to young readers. Six to eight content words are included to expand vocabulary and reading skills.Level Three books are for readers with independent reading skills. They contain 150-200 words. Longer sentences and more complicated word patterns comprise the text. Some words and illustrations may reach beyond background knowledge. Eight to ten content words are included to expand vocabulary and reading skills.