In Iranian educational system, there are special schools offering specialized curriculum for gifted students. In the curriculum of their first degree high school course, complementary contents have been provided in order to improve the process of learning. The objective of the present study has been to evaluate the content of such books which has played a pivotal role in educational process of Iranian gifted schools. We employed the triangulation method. The project was implemented between September 2014 to September 2015 by interviews and researcher-based questionnaires provided by principals, assistant principals, consultants and teachers of middle schools from gifted schools of the Isfahan province of Iran. The reliability coefficient of the questionnaire was 0.88 based on Cronbach's alpha. In order to analyze the qualitative and quantitative data, categorical analysis and descriptive statistics have been applied, respectively.Our questionnaire results showed that the four evaluated complimentary books were in quite desirable status. Based on the findings from the interviews and evidences from the gifted education literature we suggest principles by which selection and revision of complementary contents can be possible. Such principles are as follows: (i) content deepening, (ii) integrative and interdisciplinary organization, (iii) to be problem-oriented, (iv) understanding daily life use of the knowledge and (v) classification of exercises based on their complexity level.