The books written later in the Abbasid period in Iran are more anti Umayyad. Iran was Sunni at the time. There was much anti Arab feeling in Iran after the fall of the Persian empire. This anti Arab feeling also influenced the books on Islamic history. Al-Tabri was also written in Iran during that period. Al-Tabri was a huge collection including all the text that he could find, from all the sources. It was a collection preserving everything for future generations to codify and for future generations to judge if it was true or false.
Is there an answer to this question (If it cannot be answered, say "unanswerable"): What notable work of Islamic history was written in Iran during the later Abbasid period?
Al-Tabri