McGuffey's educational course begins, in the Primer, by presenting the letters of the alphabet to be memorized, in sequence. Children are then taught, step by step, to use the building blocks of their language to form and pronounce words. Each lesson begins with a study of words used in the reading exercise - the words presented with markings to show correct pronunciation and syllabification.
Through the sheer number of copies sold of McGuffey's Readers, and the length of time they remained in use, he may have had more influence upon American culture than any other educator in history. Philip Shriver, a historian associated with Miami University, credits the McGuffey Readers with popularizing "Mary Had a Little Lamb," "The Boy Who Cried Wolf," and even certain sayings - for example, "Where there's a will, there's a way."

Although McGuffey's Readers fell out of fashion in the early twentieth century, they still have a small following, even today, and can be found in use in some school districts in West Virginia and Virginia.