Culture is an inseparable part of English Language Teaching (ELT), and ELT textbooks, as one of the main instructional resources are bound to include cultural and linguistic content. However, the kind of cultural content in these books has been a controversial issue for decades. It is recommended that curriculum designers use intercultural content, which represents different countries. However, it is repeatedly observed that the cultural contents in course books are mainly drawn from some specific countries where English is the first language. In this study, the authors investigated an English textbook series named "Touchstone" to determine the representativeness of the cultural content in those books based on Kachru's (1992) three concentric circles of countries in which the English language is spoken, namely the inner circle, the outer circle, and the expanding circle. Although the results were promising and a tendency to include expanding circle countries' cultures was found, the outer circle countries were yet culturally under-represented. The findings of this research can shed light on the intercultural representativeness of this particular series of textbooks and help raise English as a Foreign Language (EFL) and English as a Second Language (ESL) teachers and learners' awareness of the cultural landscape of ELT textbooks. The findings would also benefit ELT materials developers who wish to produce course books with more internationally representative cultural content.