No one can ignore the paramount function of textbooks in teaching English. They form the basis of any course in the realm of teaching. In fact, English courses are covered by textbooks. Therefore, they should serve ELT courses in the best way as much as possible. In other words, regarding McGrath (2006), "Course book tend to dictate what is taught, in what order and, to some extent, how as well as what learners learn." (P, 171) In order to accomplish their real aim, text books should take into account different aspects of language teaching. However, we may encounter with textbooks comprising archaic topic and functions. As we have progress in the technology, we should try to accommodate textbooks into the real needs of time. For example, this fact that English language is becoming a lingua franca should reflect itself in designing different English language teaching materials and especially in textbooks. That is, as English broadens its uses and purposes, textbooks and teaching materials should provide enough room for such functions (Reda, 2003). Regarding the crucial role of ELT textbooks and English globalization, the investigation of textbooks qualification becomes an inevitable task for EFL/ ESL teachers and textbooks authors. The quality and appropriateness of textbooks emerge through such inspections like the present research. What has gone under investigation in this study is the third level English book taught in Iranian high schools. It has tried to hand out a clear picture of the textbook.