This 35-book series of basic readers is divided into five sets, each set producing progressive reading challenges for the beginner. Books teach reading skills by word families derived from similar sounds. For instance, from at, we get cat, bat, sat, etc. Each set consists of five First Volumes plus two Bring-It-All-Together review readers.Readers learn to recognize the ail/ale-sound in words such as pale, nail, scale, and wail.