Characteristics of the Shahnameh:

The history of the Iranian nation: the Shahnameh is first and foremost the history of Iran as based on collective memories of the Iranians, gathered from ancient times, modified and regulated during the Sassanian period and sanctified during the three centuries of Arab rule and influence.  By allowing his narrative to roam over the vast expanse from Kabol and Zabol and Sistan through the Persian heart-lands to the Caspian Sea at Mazandaran and again northward across the Oxus into Turanian plains, Ferdosi united in a fairly consistent whole the essential memories of that area which his contemporaries were prepared to think of as the lands of Iran.  Ferdosi succeeded in laying down the frontiers of a greater Iran, and in consolidating them on the foundation of a common past.  The Shahnameh allowed every Iranian to share in the memories of every section of his country as in a personal possession.  It helped the national consciousness to revert to patriotism with which provincial loyalties could readily merge.

Strict adherence to his sources: Although Ferdosi’s sources, as he used them, are not available to us; there are adequate reasons for believing that he faithfully kept to their content.  Ferdosi’s faithful adherence to his sources does not mean that the language was also left unaltered.  It is clear that while the form remained intact, the descriptive expressions became richer, far more expressive and necessarily expanded.

Avoidance of Islamicization: The Shahnameh stands alone among the histories of Iran written during the Islamic period in avoiding the trend by which Iranian legends and heroes were given Semitic garb or were equated with Koranic and biblical figures.   This deliberate avoidance makes the Shahnameh a truly unparalleled “Iranian national history, and partly explains its unsurpassable success throughout the periods of national revival.

Effects of poetic forms: Because the Shahnameh is a national history composed in epic form, it naturally lacks the straightforwardness and dry matter-of-the-fact nature of purely historical narrative.  It allows supernatural powers and phenomena to participate in historical events, and shows little consideration for geographic and chronological accuracy.  Ferdosi’s style is that of a superb poet.  His epic language is rich, moving, and lavish that it truly enchants the readers.  The echo of every distich, which in Persian has the rhythm of the English line: the Pharaohs of Egypt, the Caesars of Rome, is most pleasing to the senses of the reader or listener.  This is one reason for the survival of the Shahnameh.

Thus, an examination of the available evidence leads to the following conclusions:

Ferdosi followed his sources faithfully.  Some of these were anti-Arab, even anti-Islamic, some were pro-Zoroastrian, some also anti-Iranian.  When he is reflecting his sources, the statements of the Shahnameh cannot be interpreted as Ferdosi’s own beliefs.

Nowhere does Ferdosi personally use a derogatory word about Islam, and when he describes his own ideas, he has the highest respect for its founder and his family.  In the light of that fact, the Islamic names in his house (Hassan, Mansur, Qassem) become testimonies of his faith.

The evidence of the Shahnameh is in harmony with the statements of anthologists and historians that Ferdosi was a Shiite.  This is also clear from the fact that his tomb became the shrine for the Iranians in general and the Shiite in particular.

Source: Ferdowsi, A Critical Biography, by A. Shapur Shahbazi, Published by Mazda Publishers, 1991