The great importance of textbooks in the English language in the academic, pedagogic, and scientific world is uncontested. Acquiring holistic knowledge of legal transdisciplinary is of great importance to Islamic law students in Indonesia. Nevertheless, English reading proficiency of Indonesian students is problematic. The present research was to identify the genre types and unfold them through what patterns the genres are mostly structured. Data of the study were one Islamic law textbook and one jurisprudence textbook used as teaching resources and required reading at Universitas Islam Negeri Sumatera Utara, Indonesia. Based on the five main Systemic functional linguistics-based genre frameworks for the analysis, findings from the Islamic law textbook showed 18 genre types including three proposed ones under four genre families of which History genres are the most frequent ones followed by Explanation, Report, and Argument genres. On the other hand, 16 genre types including three new ones belonging to four genre families were identified in the jurisprudence in which Report genres are the most frequent ones followed by Argument, Explanation, and History genres. The commonalities and discrepancies of the findings between the two legal textbooks are assumed to be the logical results of the ideological differences and the resource aspects from which the legal discipline is oriented. The findings of the study would be useful to design teaching of reading legal English texts that can facilitate students which is unfortunately neglected by both English and law teachers.