This study aimed to investigate the readability of the fifth-, sixth, seventh and eighth-grade
mathematics course books prepared in deference to the 2017 curriculum and distributed to schools
by MEB. This study utilized the descriptive document analysis which is a qualitative research
method. Readability of the mathematics course books were subjected to a quantitative analysis by
Çetinkaya-Uzun Readability Formula. Addressing the readability levels of the texts in secondary
mathematics course books, this study performed analyses of average word and average sentence
lengths of the texts in secondary school course books. These analyses showed that there is no
linear correlation between grade level and word and sentence length averages. Readability scores
and levels of the text in the analyzed secondary school mathematics course books are not in
parallel with the grade level. Accordingly, readability scores of information and solution texts in
the fifth-grade course book were lower than the scores in other grades' course books whereas
readability scores of question texts were lower than the scores in all grades' course books but the
eighth-grade course book. Readability levels of the text in the analyzed secondary school
mathematics course book were found to be on frustration level and educational level. Course
books should also include independent texts with readability scores and level
