This paper evaluates a textbook called "Traveller 4" that is used in the second grade of secondary schools in Riyadh City, Saudi Arabia, considering its general appearance and design, objectives, content, social and cultural contexts, tasks and activities, and usefulness for developing language skills. The paper also reviews the literature concerning textbook evaluation, referring to various theoretical and empirical studies that have contributed to the field of educational material evaluation. The research used a descriptive research model to assess data regarding the assessment of the English textbook and employed a questionnaire to investigate teachers' perspectives on a range of related items. The questionnaire targeted high school English teachers in Riyadh city and consisted of 40 items, which were divided into six categories. The instrument used in this study to evaluate "Traveller 4" was the ESL Textbook Evaluation Checklist. The findings of this research study revealed important points relating to the characteristics of a good textbook and identified strengths, weaknesses, and opportunities to modify the book. This paper concludes with recommendations for improving the textbook.