The study aimed to evaluate Islamic Studies books for grade five and six from the basic education in the Sultanate of Oman based on standards of preparing the school book. To achieve that, the researcher prepared a questionnaire formed of 90 standards distributed in seven domains ( Targets - Content - Content Organization - Instructional Media Activities - Evaluation - Producing and Formatting of the book). The questionnaire was evaluated by a group of specialist for validation. In addition, Alph cronabah index was obtained and it reached (0.97). The population of the study included Islamic Studies teachers who teach five and six grades from the basic education, and Islamic Studies supervisors from Muscat and Dakhliya. The sample consisted of 140 teachers and 23 supervisors. The results of the study can be summarized as following: 1- Both teachers and supervisors agreed that the highest fulfilled standards of preparing the Islamic Studies books were those related to the domain of producing and formatting of the book for both grade five and six. 2- Both teachers and supervisors agreed that the following domains of the standards of preparing the book ( Content, Instructional Media, Activities, & Evaluation) were fulfilled moderately at both grade five and six, 3- There were no significant statistical differences between supervisors and teachers on all domains of the standards of preparing the Islamic Studies book for grade five and six. The study concluded with the following recommendations: 1- There is necessity to include the experts in Islamic science, teaching methods, instructional media, in the committee responsible of designing and preparing the Islamic studies books. 2- It is necessary to have a written guide of the standards of preparing Islamic studies books to be a framework for all committees of preparing the Islamic studies for all grades.