The purpose of this study is to evaluate readability of 9(th) and 11(th) grade geography textbooks currently used in schools. As known, one of the most fundamental features in a text-book is the readability of the text by students. In addition, it is also very important that the fluency and suitability of books match age level. In this study, the CLOZE and FOG tests were used to test the readability of geography textbooks. While the CLOZE test and FLESH formula give information largely on the level of readability of books, the FOG and SMOG formulas are being used to determine the suitability of books for age level of students. However, these tests and formulae have been developed in accordance with the grammar structure of English on the basis of lengths of syllables, words, and sentences. Thus, the Turkish application may show some anomalies. In this study, previously adopted and translated to Turkish version of the original tests and formula were applied. As conclusion, this study shows that the readability of the 9(th) and 11(th) grade geography books in Turkey is very low with respect to the CLOSE test, in medium strength with respect to the FLESH test. With respect to the FOG and SMOG tests, texts in the books are not suitable for age level of students.