The Cracking the ABC Code Learn to Read series has been designed to help children develop decoding and fluency skills. The books teach children 200 key words (taken from the Dolch list), representing 70% of our everyday language. These key words may or may not be words that children can decode given their current phonic knowledge, but are words that are frequently used and consequently important to learn in order to achieve reading fluency. The words are introduced in sets of 20 with the same key words used in different sentence structures multiple times throughout two consecutive books (e.g., Books 1 & 2, Books 3 & 4, etc). Once key words have been introduced, they are continually used throughout the series. In addition to the key words, each book uses decodable content words which children can read using their phonic knowledge. It is expected that children using the Learn to Read series already have a good grasp of the alphabet and can easily blend these sounds into words (e.g., can, fun). Each book focuses on a different digraph (e.g., ch, sh, th) and the introduction of these digraphs match the Cracking the ABC Code Multisensory Reading Level 2 books. Again, this knowledge is cumulative in that once a digraph has been introduced words containing those digraphs will continue to be used in subsequent books. Book 20 introduces the 'ai' digraph.