Humanism and socio-constructivism have entailed drastic developments in education including that of foreign/second language. Incorporating teachers and learners in all areas of education including materials development and evaluation, focusing four-pairs of binoculars on evaluating EFL materials can be taken amongst the outcomes of this trend. This study is a report of an evaluation of the ESP textbooks used in an Iranian university setting in order to investigate the extent of the compatibility of their perspectives on the ESP textbooks in general and on those in Humanities vs. engineering, specifically. To do so, about 180 ESP students and 30 teachers from Humanities and Engineering disciplines participated in the study. To collect the data, two valid questionnaires were specifically developed to measure general and specific features of the textbooks separately. Multi-method statistical analyses of the data revealed a comprehensive picture of the views of the participants on both the criteria dependability of the ESP materials in terms of content, exercises/activities, vocabulary-grammar, and physical attractiveness and maxims match. The chi-square results showed uniformities in the responses of both groups, but from the teachers’ perspectives, the books did not meet the criteria as they, holding more negative attitudes, expressed dissatisfaction with the books. On the contrary, the students showed more satisfaction with them, indicating that they meet the expected criteria of both types. ANOVA between groups’ evaluations of the data proved compatible with those of the frequency and chi-square analyses. Similarly, all of the correlation coefficients between the components of teachers and students’ questionnaires were shown statistically significant. Meanwhile, between-group paired samples t-test on both questionnaires showed significant differences between the students’ evaluations on both sets of criteria. Independent t-test for comparing teachers and students’ evaluations on both instruments sustained the results of the correlational analyses. Furthermore, both groups were found holding different perspectives as far as academic discipline was concerned: Humanities vs. Engineering. The findings, then, sustain roughly incompatible maxims towards ESP textbooks, varying views on the dependability issue, and differences as to componential analysis of the criteria. Pedagogically, the findings suggest student involvement in the process of syllabus design and materials evaluation, and preparation in general and ESP, in particular.