An instructive and learned review here by Malise Ruthven about a book previously noted on CLR Forum, Hamid Dabashi’s Shi’ism: A Religion of Protest.  One note of particular interest was the, for lack of a better term, gnosticism of Shi’ism highlighted by Ruthven.  Here is a bit from the review:

The crucial difference between Shias and Sunnis is not so much in the letter of the law, which Sunni legal scholars interpret in accordance with a hierarchy of sources embracing the Koran, the Prophet’s custom (sunna), consensus, and analogical reasoning. It lies rather in the quasi-mystical authority with which the Shiite legal scholars are invested.

In the Sunni tradition the ‘ulama, or legal scholars, came to act as a rabbinical class charged with the task of interpreting the Koran and the ethical teachings derived from the Prophet’s exemplary conduct as recorded in hadith reports or “traditions.” The eventual division of the mainstream Sunni tradition into four main schools of law allowed for considerable variations in interpreting these canonical texts. The mystical or “otherworldly” aspects of the Prophet’s legacy became the province of the Sufi or mystical orders that grew up around the myriads of “saints” or holy men.

The Shias, by contrast, institutionalized the Prophet’s charisma by investing their imams with special sources of esoteric knowledge to which they, through their religious leaders, had exclusive access. Hence Shiism, arguably, presents a more unified approach to Islam than Sunnism, though one that (like Protestantism) is opposed to the mainstream. During Islam’s formative era most of the holy and sinless Shiite imams in the line of Muhammad were deemed to have been martyrs or victims of the usurping Sunni caliphs. After the twelfth imam in the direct line of Muhammad finally “disappeared” in 940, Shiite authority came to be exercised by a formidable clerical establishment—comparable to the Catholic priesthood. These religious specialists were assumed to be in possession of the esoteric knowledge and interpretive skills necessary for the community’s guidance. The parallels with Christianity are striking. For the people called Ithnasharis, or Twelvers (who comprise the majority of the Shia), the disappeared or “Hidden Imam” is a messianic figure who will return (like the resurrected Jesus) to bring peace and justice to a world torn by strife.