How Authentic is the Language Presented in EFL Textbooks?

My experience as an EFL teacher has provided me with sufficient knowledge on how important EFL textbooks are for language learners as the primary source of the target language. When I started my career as a university instructor in 2006, I was much concerned with the authenticity of the language presented in these textbooks. I found a possible solution to this problem in Corpus Linguistics. Based on the evidence obtained from a large reference corpus, the British National Corpus, multi-word units, such as fixed expressions, idioms and collocations presented in the Egyptian Secondary School EFL textbooks were analyzed to determine how authentic these units are. The results were somewhat disappointing concerning the occurrence of awkward expressions as well as the extremely low percentage of explicit presentation of these units compared to their significance in raising learners'' language proficiency through raising their awareness of the special nature of the connections between different lexical items. The book raises an alarm on how these textbooks are designed and evaluated as a primary source of knowledge for language learners.