This book consists of 419 treatises, dating back to the Buyid dynasty’s subjugation of the Abbasid Caliphate. These treatises are important documents preserving a large quantity of primary material that benefit greatly the study of Islamic State’s history under Buyid control (334-447AH / 946-1055AD). The treatises expose the ongoing conflict between the Buyid and the caliphate establishment and surrounding forces. They also reveal the internal competition within the Buyid dynasty itself. The collection provides insight into political correspondences, economic organisations, and administrative protocols. It also includes documentary records, treaties, and letters of appointment to prominent state positions. The reader will find a treasure trove of extensive benefit. Researchers will find in them a large volume of novel historical material published for the first time. This includes rich primary sources that contribute to new studies and findings in the field of history. Rasā’il al-Ṣābī are mostly official administrative treatises issued by Abbasid caliphs or Buyid governors; the latter had seized large swathes of territory in the Islamic East, putting them outside caliphate authority. They successfully appropriated the worldly powers of the Abbasid caliphate and controlled state resources. These treatises reveal their views on the concept of state, philosophy of administration, as well as their economic, administrative, political, military and urban policy. They also provide insight into the Buyids’ relationships among caliphs and civilians, and into their social and cultural history.