What are the best sources for understanding the history of the khilafah (caliphate)?

In a Nutshell: The best sources are the earliest texts like those of al-Tabari's "Tarikh al-Rusul wa al-Muluk" (History of the Messengers and Rulers) and al-Baladhuri's "Futu al-Buldan" (Conquestions of Lands) both written in the 10th century. Others worth considering include: al-Yaqubi's "Tarik al-Yaqubi", al-Masudi's "Muruij al-Dhahab wa ma'adin al-Jawhar" (Places of gold and mines of gems) and Ibn Khaldun's "Muqadammah". Introduction There are a number of historic sources that provide important insights into the caliphate, its political, social and economic dimensions, upon which many later books of history were based. The sources can be split into classical Islamic works and more contemporary modern research texts. Classical Works One of the earliest sources was that of the historian al-Tabari (d. 923) "Tarikh al-Rusul wa al-Muluk" (History of the Messengers and the Rulers), a universal history starting with Creation, messengers and prophets and finally the emergence of Islam. Tabari provides a wealth of detail on the seerah and the caliphates that followed over the first three centuries. The next source is al-Baladhuri (d. 892), a contemporary of al-Tabari, who wrote "Futuh al-Buldan" (Conquests of Lands). This work focused on political and military events with less discussion in relation to social and economic conditions. The historian al-Yaqubi's "Tarikh al-Yaqubi" (Yaqoubi's History) is a more modest but critical endeavour from a Shi'a perspective, rejecting the early caliphates deeming them to be "muluk" (temporal rulers), using the term "Caliph" or "Caliphate" for Imam Ali (ra) and his son Hasan. The geographer, historian and traveler al-Mas'udi (d. 956) wrote "Muruij al-Dhahab wa Ma'adin al-Jawhar" (Places of Gold and Mines of Gems) and "Kitab al-Tanbih wa al-Ishraf" (Book of Warning and Revision) cover a lot of ground on the culture and beliefs of peoples across the Caliphate. The Shafi'i jurist Mawardi's (d. 1059) "al-Ahkam al-Sultaniyyah" (The System of Governance) written in opposition to the Fatimid Caliphate pretender is significance in its theoretical analysis of the Caliphate, covering the duties and rights of the Caliph and the ruling structure. Much of it is influenced by the Abbasid structures of governance however is one of the best clear articulations of the subject by a historian and jurist. A late fourteenth century work is Ibn Khaldun's (d. 1406) magnus opus, the "Muqaddimah", covering the history and historiography relating to the caliphate. Other works include Ibn Hazm's "al-Fasl fi al-Milal Wa al-Ahwa Wa al-Nihal" that provides a comprehensive account of the Caliphate, Nizam al-Mulk's (d. 1092) "Siyasatnamah" and ibn al-Tiqtaqa's (d. 1261) "Systems of Government and Muslim Dynasties". Contemporary Works Contemporary works comprise those produced by Orientalists and Arab scholars, both of which usually depend on classical works. One of the earliest works is William Muir's "The Caliphate: Its Rise, Decline and Fall" which comprises a comprehensive study of the history of the Caliphate from its beginning upto its decline. Thomas Arnold's "The Caliphate" considers the origin of the Caliphate, the titles of the Caliph, the Abbasid and Ottoman eras, whilst considering the juristic justification of the Caliphate via the Qur'anic and Sunnah traditions. Professor Barakatullah's book "The Khilafah" written in 1924 is a serious study of the history of the Caliphate. He also considers the political, and theological perspectives adding personal observation of the Muslim countries of his time to contribute to the discourse of his time seeking restoration of the Caliphate. One of the most detailed and extensive research relating to the Caliphate was carried out by the Palestinian jurist and Shari'a court judge Taqi al-Deen al-Nabhani, founder of the group Hizb ut-Tahrir, which seeks to re-establish the Caliphate to resume Islam. Nabhani produced a series of texts detailing the history of the Caliphate, how it was first established, structured during the life of the Messenger in Medina, how it operated historically, the juristic evidences underpinning it and its various systems, how it declined and how it should be re-established for a contemporary age, including a detailed constitution. Rashid Rida's "al-Khilafah wa al-Imamah al-Kubra" was an Arabic text covering the history of the Caliphate, relying on earlier sources, adding little new to existing works. Dr. Muhammad Musa's "Nizam al-Hukm fi al-Islam" (System of Rule in Islam) and Ali Husni al-Kharbutli's "al-Islam wa al-Khilafah" (The Caliphate and Islam) rely on earlier Muslim works and sources along with contemporary Orientalist contributions. Al-Kharbutli's book interestingly discusses the Caliphate in its judicial, philosophical and historical framework, considering the views of various Muslim sects and critically considering its historical record from inception to final demise in 1924. A more controversial work was that of the Egyptian jurist Ali Abd al-Raziq "al-Islam wa Usul al-Hukm" (Islam and the Basis of Rule) published in 1925. al-Raziq for the first time in history advocated ideas, similar to those raised by Sayyid Ahmad Khan of India (d. 1898) and his colleague Shibli Noumani, claiming the Caliphate had always been a misfortune for Muslims and Islam had never ordained any form of governance. He was heavily criticised and condemned by the jurists of his time and expelled from al-Azhar University. References al-Tabari, "Tarikh al-Rusul wa al-Muluk" (History of the Messengers and the Rulers) al-Baladhuri, "Futuh al-Buldan" (Conquests of Lands) Ali Abd al-Raziq, "al-Islam wa Usul al-Hukm" (Islam and the Basis of Rule) Ali Husni al-Kharbutli, "al-Islam wa al-Khilafah" (The Caliphate and Islam) al-Mas'udi, "Muruij al-Dhahab wa Ma'adin al-Jawhar" (Places of Gold and Mines of Gems) al-Mas'udi, "Kitab al-Tanbih wa al-Ishraf" (Book of Warning and Revision) al-Yaqubi, "Tarikh al-Yaqubi" (Yaqubi's History) Dr. Muhammad Musa, "Nizam al-Hukm fi al-Islam" (System of Rule in Islam) Faisal al-Kathiri, "Succession to the caliphate in early Islam" Ibn al-Tiqtaqa​​​, "Systems of Government and Muslim Dynasties" Ibn Hazm, "al-Fasl fi al-Milal Wa al-Ahwa Wa al-Nihal" Ibn Khaldoon, "al-Muqaddimah" Mawardi, "al-Ahkam al-Sultaniyyah" (The System of Governance) Nizam al-Mulk, "Siyasatnamah" Professor Barakatullah, "The Khilafah" (The Caliphate) Rashid Rida, "al-Khilafah wa al-Imamah al-Kubra" (The Caliphate and the Greater Imama) Taqi al-Deen al-Nabhani, Nizam al-Hukm (The Ruling System) Taqi al-Deen al-Nabhani, Dawlah Islamiyya (The Islamic State) Taqi al-Deen al-Nabhani, Institutions of State in the Khilafah Taqi al-Deen al-Nabhani, The Draft Constitution Vol 1/2 Thomas Arnold, "The Caliphate" William Muir's "The Caliphate: Its Rise, Decline and Fall"