This study aimed to find out whether the microstructural approach of schema theory (MICAST) can be employed to evaluate the reading passages of textbooks. To this end, the macrostructural approach of schema theory (MACAST) was utilized to assign twelve passages of a textbook taught at the upper intermediate level of language proficiency to descriptive, expository and narrative rhetorical modes generally knows as genres. All the words constituting the passages were then treated as schema tokens and assigned to their linguistic domains, genera, and species as suggested by the MICAST. Subjecting the tokens constituting the three genres to statistical analyses showed that the genres differed significantly from each other. They did not, however, differ significantly in the number of passive schema tokens they contained. The descriptive, narrative and expository genres did also differ significantly from each other when their constituting schema tokens were reduced to exclusive schema types. The administration of a flow perception questionnaire to the readers of the passages showed that among the genres, the descriptive one induces flow the most because its exclusive semantic, syntactic and parasyntactic schema types were significantly fewer than those of narrative and expository genres. The pedagogical implications of the findings in the realm of English language teaching are brought up.