This study reports on the analysis of a widely used "General English" textbook to explore the relationship between lexical bundles included in the text and lexical bundles identified in relevant corpora to determine the appropriateness of the text's vocabulary in relation to its stated objective. Appropriateness is examined through the analysis of usefulness and functions, and the relationship between the two, by comparing the usefulness scores of various functions. The results show a relatively low level of usefulness of the lexical bundles in the textbook, meaning low frequency and small range of usage for the analysed items. The function analysis showed that textbook includes all the functions. The most common function was referential, followed by stance, special conversational, and discourse organizing functions. The current study offers an initial step for future research of lexical bundles and their functions, and usefulness in language teaching and teaching materials development; specifically, it suggests a possible methodology to be used in such research. Moreover, the results of this study provide insights into the value of lexical bundles in teaching and the development of teaching materials.