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.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): What are the books written early in the Abbasid period like?
unanswerable