The Shahnameh of Ferdowsi, an epical poem book of over 55,000 couplets, is based mainly on a prose work of the same name compiled in the poet's earlier life in his native Tous. This prose Shahnameh was in turn and for the most part the translation of a Pahlavi (Middle Persian) work, a compilation of the history of the kings and heroes of Iran from mythical times down to the reign of Khosrau II (590-628 A.D.), but it also contains additional material continuing the story to the overthrow of the Sassanids by the Arabs in the middle of the 7th century A.D. The first to undertake the versification of this chronicle of pre-Islamic and legendary Persia was Daqiqi, a poet at the court of the Samanids, who came to a violent end after completing only 1000 verses. These verses, which deal with the rise of the prophet Zoroaster, were afterward incorporated by Ferdowsi, with due acknowledgements, in his own poem.
After Ferdowsi's Shahnameh a number of other works similar in nature surfaced over the centuries within the cultural sphere of the Persian language. Without exception, all such works were based in style and method on Ferdowsi's Shahnameh, but none of them could quite achieve the same degree of fame and popularity.
Some experts believe the main reason the Persian language today is more or less the same language as that of Ferdowsi's time over 1000 years ago is precisely because of the very existence of Ferdowsi's Shahnameh. In other words, the Shahnameh itself has become the main pillar of the modern Persian language. Studying Ferdowsi's masterpiece also became an absolute requirement for achieving mastery of the Persian language by all the subsequent great Persian poets, as evidenced by numerous direct and indirect references to the Shahnameh in their works.
There are several aspects of the Shahnameh that are remarkable. One is that it is one of the few original national epics in the world. Many peoples of the world have their "own" national epics, but more often than not, the original theme of such national epics are borrowed from other cultures (usually from neighbouring cultures). This is not the case with the Shahnameh, which is based on the original Iranian stories. Another remarkable aspect of the Shahnameh is the language element itself, which is nearly pure Persian, and yet very much natural. After studying the Shahnameh, one can clearly see that Ferdowsi must have had a solid command of the Pahlavi language (Middle Persian) as well, with an astonishing linguistic understanding of the transitional patterns from Middle Persian to Modern Persian. Yet another important aspect of the Shahnameh is the honesty with which the author has delivered the stories without allowing his personal views enter or alter the original story; in this regard, if he has had something to say, he has said it on his own account and in between the narrations of the original stories. The language that Ferdowsi has used is uttermost clean and free of any vulgarism or offensive words or expressions. That, combined with Ferdowsi's unparalleled artistic and linguistic magic, has produced a masterpiece which has captivated its audiences for over a thousand years now. Many Iranians consider the Shahnameh to be their true certificate of national identity.