What a large title. Well, as we know the main center of islamic scholarship was the great library in bagdad, held by the abbasid iraqis that followed the sunny branch of islam. Iran had a lot of trouble between sunnis, shias and zoroastrians, but at the end the shias became the majority. Based on that I want to ask something: What is the most likely outcome to the library and the city of shia persians capture Bagdad? In OTL the closest (AFAIK) that the persians came to take the city was during a saffarid campaign and it was repelled. Even if they marched on the city the Saffarids were sunnis so they most likely would absorb the abbasids as tributaries and leave the city as it.
I want to make clear that I'm not expecting that the shias would do something bad to the city, I only expect minor changes like they replacing sunni scholarship with shia one, or maybe not even that. I just want to know your opinion on the subject because I'm just too unliterate on it...