Ann K. S. Lambton 
State and Government in Medieval Islam [PDF ebook] 

First published in 2004. For the Muslim the foundation from which all discussion of government starts is the law of God, the sharī‘a. Theoretically pre-existing and eternal, it represents absolute good. It is prior to the community and the state.‘ Part of London Oriental Series, this volume’s concern wis with the political ideas of the period extending from the 2nd/8th century to the 11th/17th century and to the central lands of the caliphate, including Persia, and North Africa.