In spite of the existence of several educational resources in the field of language teaching as well as the quick growth of advanced technologies, educational textbooks still play a major role. This explains the significance of designing and evaluating textbooks in countries where language instruction is highly textbook-oriented. The present paper reports the results of a summative evaluation of the textbook 'Prospect 1' which is employed across the nation for zero beginners at junior high school. To this aim, the motivational design of the book was evaluated using Keller's ARCS model recognized as one of the most effective models. Based on the analysis of the survey and interview data it was observed that in general the students' motivation for this book is desirable. The findings also indicated that this book is more effective in the Confidence area followed by Relevance. On the contrary, it was found out that the students' Satisfaction and most of all Attention were not desirable. The findings of this study verified in general that this book has a suitable motivational design. However, it is suggested that the related amendments for improving the desirability for the Satisfaction and Attention areas be implemented.