I have experienced situations in elementary education, and adult basic education, when a student is reading each word in a book perfectly, however; they may not have actually understood what they were reading. When questions were asked about the story or subject matter, it becomes obvious that the student did not comprehend what they read.
In adult education, many times students will come into the classroom as non-readers. They have very low self esteem, are sometimes very frustrated, and may think they will never be able to read.
In these situations, it is best to start the student with low level elementary material, then build upon that foundation. This plan cannot be accomplished in a short amount of time, so it is important to try to stay positive and encourage the student(s).